You'll need to play the game a few times to rack up enough kills (pig points) in order to buy the game's active and passive perks from the Fed. There's little point talking about how to get a huge kill count until you do this. Having all the perks switched on is the only way you're going to stand a chance of getting past 100 kills..... and obviously don't turn the cheat on - that's just - well... cheating.

You can rack up enough pig points legitimately by actually playing the damn game.
If you're an annoying little impatient kid with ADHD and don't want to be eased gently into the game, you can even hack the game's save file to give the necessary pig points to yourself.

Hurry up and get all them perks enabled now. I'll wait....

First off, there's a basic strategy guide in the starting bedroom once you purchase it for free, so have a look at it for some tips.

The mouse handling in this game is absolutely atrocious so you will need to adjust your mouse so the sensitivity is way down and then adjust your mouse DPS so that it's way up. Widescreen displays seem to make it worse - and honestly this is the worst thing about the game.

Here's what I noted about the gameplay: There's essentially two things you need to keep in mind when playing. That is:
(a) Situational and environmental awareness and
(b) prioritising the enemies you aim at by their deadliness.

You have four weapons available:

1. Blicky
Your default Blicky holds 30 rounds before you need to reload. You will do most of your work with this. There's no need to use anything else really for the first 100 kills. Make sure you remember to reload often when you aren't under immediate fire to keep your clip full.

2. Sniper Rifle
It is good at shooting from a long distance, and can be useful in dealing with the red enemies early on. It's also helpful in clearing the map of annoying handgun enemies and it will KO them in one shot.
Other enemies will require a few hits though.

3. Auto Rifle
This weapon fires very fast rounds and becomes incredibly useful when there are really too many enemies on the street. If you feel that you've lost control of the population, this is the time to pull it out. A good landmark for pulling it out is when you see too many red sniper lasers. It's also useful for the occultist boss.

4. Rocket Launcher
This weapon is best reserved for Gattling and K4-C9 bosses mainly. Mind that you can kill yourself with it's splash damage - if you aren't careful. Remember to wait for it to reload after using it so you can pull it out and fire it immediately for the next emergency. Otherwise you will be left waiting for it to reload when you're being ripped to shreds.

No you can't hit the helicopters with it. Yes I know that it makes no sense, but the helicopters don't shoot at you anyway.

1. YOU NEED TO KEEP MOVING. Staying still equals death, especially with too many snipers and katana enemies on the map, but even then in general anyway. You can get away with standing still when the population is low, but when there are many of them, standing still to aim at them will get you killed. You will need to run-and-gun. Camping inside your house is never going to work because of the snipers that can shoot you through walls - and that's why they're in the game and able to do this. Camping typically spoils games like this, and the game doesn't want you to camp.

2. Keep the population on the map down to a minimum. The less enemies there are, the less you will be overwhelmed by them - and hence the easier time you will have of dealing with them, and the faster you regenerate health from your passive perk from killing them. This means that your first order of business should be clearing them, not running away or camping. There is a temptation to run around the map avoid the enemies and avoid shooting them to let your perks regenerate. If you do that, loads more enemies will show up to overwhelm you. You need to be constantly hunting and killing to keep your health up and threats down.

3. Given that headshots appear to do more damage, you should aim for their heads.

4. Also remember that cop cars block all bullets, so it makes sense that you hang about the center of the map and to just one side of the cop cars down the street a bit as you circle around. What tends to happen is that the enemies that spawn at the other end typically have crappy AI and can't navigate their way to the other side of the cop cars where you are.
Note that you can also push the cars around and over to form a barricade of sorts. The only bad thing about cars is that they can block your view of possible grenades on the ground between them.

5. The rocket launcher should be used with EXTREME caution and precision. An ill-timed rocket firing that blows up in your face from hitting an enemy or object too close can wreck your game. Honestly it's the easiest way to die in the game if you are not careful. Yes it can clear most bosses in one hit, but your chance of missing moving targets is pretty high too - so aim at their legs and the ground under them from up high. For that reason, rockets are best reserved for the red gattling boss and green K9-C4 boss later in the game. Note that the green K9-C4 pig boss, and the occultist pig boss don't move from their spawn points at the end of the street - making them easy targets.

If you are using the invincibility perk, you can also shoot at the ground under your own feet to kill all those enemies chasing you around. You might fly into the air, but you will walk away unscathed! That's a handy "hail mary" for you to remember. Otherwise never, I repeat NEVER use the rocket launcher unless you are either airborne or firing down from on the roof of a house. The chance of blowing yourself up with it is too great - as is missing your target.

Rockets are also good for crowd control. When too many enemies get onto the map and bunch up, letting off a rocket can rack up your score very nicely, and becomes increasingly important once you rack up over 120 kills, because the cop spawn rate will increase to the point where you can't control them.

6. The other easiest way to die is to get taken out by a grenade fired from an enemy with a launcher. Grenades will kill you in one shot if you are too close. I've had many a good run ended just because one of these blew up right behind me. The biggest problem with them is even seeing them, as in many cases you will not even notice that they are even there. Keep an eye on where those grenades are and GET AWAY FROM THEM. It can be tricky as they can land behind cars and fences. That's why you need to keep moving and keep an eye out for them on your six.

7. The house and car roofs are useful to put some distance between yourself and ground bound enemies (like dogs and non-boss katana wielders mostly). However grenades and bullets can still hit you up here - so it's not a solution to all your problems. With some practice you can jump from roof to roof too. Camping on the roof is possible to avoid dogs, but getting off the roof to pick up loot is the tricky part because down below will be a few remaining dogs and probably a gang of katana enemies waiting for you. Stay on the roof and let loose with some sniping and rockets until you can recharge your invincibility, then get off the roof - use your invincibility perk - and clean up any remaining dogs and katana enemies with the auto rifle, or blow yourself up with the rocket launcher while invincible and send all those personal-space invaders to hell.

8. Remember your active perks to get yourself out of a tricky situation. Health regen should be used when your health is down to around 1/4. Trouble is that you will end up using it too late most of the time and not only waste the opportunity, but get wasted yourself. Invincibility is useful when tackling a gattling gun pig, dismounting from a rooftop into dogs, and when there are too many katana cops around. Of course the perks have a cooldown period so don't waste their use. Only use them when you are in dire trouble.

9. Always keep an eye on your six and watch your surroundings. You don't want the dangerous bosses and katana cops to sneak up on you from behind - and you much less want to get hit by a grenade you didn't notice behind a car or a fence. Keep moving around in circles so you can see things coming, and don't waste too much time and focus trying to kill an enemy while being unaware of other threats sneaking up.

10. Rolling gives you invincibility frames of animation. You need to be doing a lot more of it. Especially handy when it comes to dodging dogs.

11. The game allows you to aim your gun with the right mouse button. It's pointless to do this with your Blicky because you already get sights when you fire with left mouse anyway. Using right mouse just slows you down and you can't afford to slow down in this game. Right-mouse aiming is really only useful with your other weapons - particularly the launcher.

12. Keep the door shut at the back of your house. The initial enemies in the back yard at the start of the game can get stuck there and that's just fine and dandy to help you clear out the more threatening enemies in early stages.

13. Tactical cocaine slows all enemies down - but it also slows you down, except your aim. This is really only helpful when aiming rockets. Since the enemies won't be moving around very much, you can easily line up the boss pigs (particularly the gattling boss) with a rocket and not miss so easily when they are a good distance from you.

* Handgun cops

These guys are the least of your worries once you have all your perks. They sting a bit, but roasting them gets you the health back thanks to your perks. Try this sometime: At the start of the game, just stand out in front of the house and don't shoot any cops. No matter how much those pistol cops shoot you, with all your active and passive perks turned on they just won't be able to kill you.
Get close to them so you don't miss your shots and waste time trying to aim at them with your pistol from a distance. This clears them up quickly. Otherwise, the damage other pistol and rifle cops cause can be largely ignored until you have nothing else to shoot at. When there's no real dangerous cop, shoot at them simply to keep their population down.

* Snipers

These guys have sniper rifles shoot through walls, so finding out where those red laser dots are coming from and taking them out is typically your first order of business when you have to choose between targeting them or ordinary handgun cops. Keep moving and they have trouble targeting you though. Your biggest problem is when there are too many on house roofs because then they can do some damage. If you see too many red lines for your liking, consider pulling out the auto rifle to target them and clean up the map a bit.

* Auto-rifle grenade launcher cops

More deadly than any other cop, because their grenades can kill in one hit. However, they can't really hurt you aside from the occasional auto-rifle fire. Just get those grenades stopped though. Note that sometimes these guys will spawn on rooftops, which makes finding and targeting them tricky.

* Katana cops (non-boss)

These guys have swords and chase after you fairly quickly trying to hack you up. They can't actually hurt you if you keep running away from them, but beware that they don't surround you and gang-bash you. A good tactic is to jump over a fence or onto a house roof if there are too many of them. That will confuse their AI for a bit and give you some time to get distance from them. Otherwise if you keep running away from them they can't really hurt you. They will hurt if you stop to shoot other pigs though, so they will force you to keep running and gunning - as you should be doing anyway. As they don't actually fire at you, you can keep them alive for quite a while and run away from them - killing off more threatening pigs while they chase you.
To kill them off you can backpedal and circle around to the right and you'll miss most of their sword swings. Best do this in an open area, because you don't want to backpedal into a fence, get stuck, and then hacked to death. Also consider using the auto rifle to mow down a gang of them. It's too hard with the blicky.
If there's a lot of them, you can jump up onto a house roof and let a rocket go, but be careful that you're nowhere near the blast. Just being on the roof directly under a blast can wipe you out.
Your last resort - if they surround you - is to activate your invincibility and become a suicide bomber by blasting the ground with a rocket. That will kill the lot of them in one shot. If you do get stuck in a corner, you won't have much time to react with invincibility though.

These are way more deadly than ordinary cops and their entrance is signalled by that damn annoying football horn. These guys should become your top priority targets once they make an appearance. When you hear that horn, you should immediately look to find where they are and which one it is. This is a good time to use your other weapons - if you have them. Top tier bosses are more easily wiped with rockets. You want to knock them out ASAP so you can get back to clearing the map of other annoying cops with your pistol. These guys will always drop extra weapons and you'll need them and their ammo to tackle future bosses. Conserve your sniper, auto rifle ammo and rockets for bosses as you don't get much of it when you find it.

* Katana Pig Boss

This blue guy flies through the air, but he can get stuck behind houses where he can be ignored for a little while - but you will find him spawning reliably in the back corner of the map. Essentially you want to shoot him as he gets near overhead and his swings initially miss you from too high up. You'll need to be back-peddling and turning around in circles to the right - that will help you avoid his swings as he is right handed. Taking more than one whack from him can put you in danger - and this can happen easily if your backpeddling is being blocked by fences, bushes and hedges. Your safest bet is to kill him as soon as you can in an open space at one end of the street. Auto rifle is best but but your blicky works just as well as his health isn't as great as the other bosses. Rolling out of the way to dodge the sword blows will keep you alive. Note that he can knock cars over too.

* Gattling Pig Boss

This big red cop really sucks. In the game's initial stages - before you have any rockets - your only hope is to hide behind a cop car and shoot at him from behind it with your Blicky or better yet a sniper rifle if you have one. The cop cars will give you cover from his minigun rounds - but this guy will take a lot of shots from the Blicky. Note that this guy can knock over cars if he's too far away from you, otherwise he'll get stuck behind one for you to shoot at. Otherwise if you are exposed with no cover, his minigun can quite easily rip you up.

Later in the game, hiding behind a car to shoot at him is more likely to get you killed. There will likely be a large number of pigs, especially katana pigs, and grenades flying about. Then you will need to dispatch this guy as soon as you can. Best way to do this is with the rocket launcher. Get behind a car and give yourself some distance from him as he moves to the center of the map. Triple-jump into the air over the car, and use right mouse to aim at his legs or at the ground just in front of him. Fire the rocket and immediately reload the launcher. You can then switch back to your blicky once it's done. This takes some practice, and you will absolutely need to reload that launcher so you can use it in a pinch for next time.

Mind that this boss does move about, so the chance of you missing with a rocket is pretty good. If he's too far away, using tactical cocaine will slow this guy down from moving - letting you target him better. If you miss, you are going to be in trouble however. Taking extra time to reload that launcher will leave you exposed, and valuable time to kill increasing cops will be wasted.

You can use immunity to attack him without relying on cover - but there's a risk that you won't kill him before immunity wears off. It's a last resort tactic though. It may be useful to use immunity to get close to him and blow him up (and yourself) to take out a lot of pigs on the map if you wish to cut their numbers too.

* K9-C4 Pig Boss

This green guy sets wave after wave of exploding dogs onto you, and typically only starts showing up when you've been playing long enough to have passed 80 kills or so. His dogs will home in on you and explode on you when they get close enough. Fortunately he doesn't really chase after you or move, which makes him easily targeted by sniper rifle fire from the roof - but given that's not powerful enough - you will want to use the rocket launcher on him. You can either do this from safely from the top one of the house roofs, or by triple-jumping in the air. You just really need those dogs to stop however, so killing him as soon as you can is your top priority. The rockets also do collateral damage to dogs nearby him which is why rockets are preferred.

* Occultist Pig Boss

This purple guy only shows up when you're doing exceptionally well (past 200 kills AFAICT)
He puts on his robe and wizard's hat and blasts you with mighty disable perks of the beyondness.
Like the K9-C4 pig boss, he doesn't move - so targeting him with the rocket launcher is easy. Otherwise take out your assault rifle and kill him ASAP.

Any other tips or tricks, please let me know. Best I can manage is around 163 cops in v1.1.1 which is not that bad but apparently still pretty low compared to those who have cleared more than 500 in this game's big John-Thomas swinging pissing contest.

I would be happy to hear of any exploits and glitches to get well beyond this. I'll update the guide to reflect anything new I learn.

And yeah - no idea about the garage you need a code for. I think it's just left over from when they ripped the map out of cuckold simulator. I'm sure you can hack the game and find out what's in there yourself.