This guide isn't totally inclusive on how to get everything you need in the game, just the conditions you'll need to meet for getting each ending. I just made it because I couldn't find one. If you're ever stuck in the game, check your map for any covered up areas you may have missed...

⚠️⚠️⚠️ MAJOR note about Ending 4: ⚠️⚠️⚠️
Ending #4 can be missed in a save file and best done first if you want all of them.

No pressure for endings 1, 2, 3, or 5:
There's no way to lock yourself out of getting any of these endings at any later time, and the further you are into the game and the more items and skills you get, the easier it will be to circle back and get them, so no pressure at all. If you'd rather just play and enjoy your time after getting ending 4, have fun. Just use this guide if you're stuck.

The endings go in order of 5 to 1 from easiest to hardest.
Ending 5 can be gotten the earliest, but least rewarding and Ending 1 requires a lot of set up, but most rewarding ending with Ending 1 being the "true ending".

Conditions:
1. Find Cheshire cat's room and talk to her, ask her how to leave this world and tell her you want to go.

Q&A:
Q: Where can I find the Cheshire cat's room?
A: Near the mansion entrance, in a room where the floor is a circular plate (maybe a table?), with two grand staircases and a red rug leading to a door in the background, there's a crack in the floor near the east wall.

Note: You might be able to get this ending later in the game by accepting the Cheshire's offer to leave this world if you find her in the Castle's mirror room, too, but just talking to her in her room is the easiest way.

Conditions:
1. Do NOT catch Alice before she reaches the Queen's Castle
2. Most important thing NOT to do for this ending: Don't 👏 get 👏 the 👏 key 👏 from 👏 Dodo. Either ignore her completely or defeat her in combat twice. Don't pass her speech checks and don't do her quests, she will force the key on you if you do. Getting the key from Dodo will lock you out of this ending for the rest of the save.
Side note: if you beat her twice in combat and it's early game, she should disappear from the world, that's normal. You won't be able to complete Dumpty's quest without Dodo, but that's OK right now.
3. Make your way to the Castle and defeat the Queen of Hearts.

Q&A:
Q: I already have the key from Dodo, can I do this ending?
A: Unfortunately, no, not for that save file, but it is possible to get the achievement by doing it in a new game save slot.

Q: What if I catch Alice?
A: Unless you know the trick on how to catch her, you don't have to worry about this.

Conditions:
1. Do NOT catch Alice before she reaches the Queen's Castle
2. Talk to Dodo and convince her to come to the tea party
3. Get the key from Dodo at the tea party.
4. Make your way to the Castle and defeat the Queen of Hearts.
5. Use Dodo's key on the room behind her throne and confront Alice.

Q&A:
Q: I didn't pass the speech checks with Dodo and beat her up twice, now I can't find her at all, what can I do?
A: If you already got Ending 4, she won't disappear from the Library on top of the mansion and you can still talk with her... I think. Try leaving and visiting the library again. If you haven't gotten Ending 4 yet, and Dodo has disappeared from the Library and world completely, you're on track for getting Ending 4, unfortunately.

Q: What if I catch Alice?
A: Unless you know the trick on how to catch her, you don't have to worry about this.

Precondition:
1. Get Ending #3 so time rifts appear.

Conditions:
1. Do NOT catch Alice before she reaches the Queen's Castle
2. Get both Dodo and Humpty to the Tea Party
3. Restore the Hatters memory with the 「 Hat of Truth 」
4. Talk to Dodo, then Humpty, and convince them to leave this world.
5. Meet Cheshire in the mirror room of the Castle, east of the Castle Hall fast travel location and up.

Q&A:
Q: How can I get the「 Hat of Truth 」?
A: You must first close all time rifts. Closing the last rift will reward you with the key to the Castle dungeon. Take that to the dungeon and head deep inside...

Q: What if I catch Alice?
A: Unless you know the trick on how to catch her, you don't have to worry about this.

Q: How can I convince Dodo to leave?
A: After convincing Humpty to leave, you can suggest that Dodo go to Humpty's world.

Q: How can I convince Humpty to leave?
A: Pass a speech check with her.

Precondition:
1. Get Ending #3 so time rifts appear.
2. Have the Teleport ability (see Q&A below if you need it)

Conditions:
1. Catch Alice before she makes it to the Castle!
2. Get both Dodo and Humpty to the Tea Party
3. Restore the Hatters memory with the 「 Hat of Truth 」
4. Talk to Dodo, then Humpty, and convince them to leave this world.
5. Meet Cheshire in the mirror room of the Castle, east of the Castle Hall fast travel location and up.
6. Defeat the final boss!

Q&A:
Q: How can I catch Alice?
A: Use the 「 White Watch 」 in your inventory to start a fresh timeline, use the teleport ability immediately from the start to go to the fast travel location "The Mushroom Forest", this will put you next to the Humpty's Wall where you fight her the first time, then head left (note: heading right will make you fight Humpty and you won't be able to catch Alice unless it's the first, immediate thing you do), you should bump into Alice right before you get to the small door to the Tea Party area.

Q: How can I get the teleport ability?
A: Meet Cheshire in her room and befriend her by talking to her, leaving the mansion and coming back to talk to her more until her affection is maxed out. Eventually she'll ask if you want to be friends, even in other timelines, and she'll give you the item 「 Cheshire's Bracelet 」 as proof of your friendship. Once you have the bracelet, use the 「 White Watch 」 in your inventory to turn back time and choose 'lend us your power!' when you talk to her, even if you fail the check, she'll notice your bracelet and help you.
Things I'm not sure about:
- Passing the hard speech check for 'lend us your power!' might also get you the ability.
- I'm not sure if having the bracelet is a requirement for the ending or not, it's a good idea to just pick it up at this point.
- Getting the bracelet might not be possible until after the events of getting the 「 Hat of Truth 」, I think maybe Cheshire has to figure out the main characters can time travel, first.
Note: You'll need a red crystal to activate this ability, but it's well worth it, because the ability will let you fast travel on your map screen to any fast travel location now! Super handy to get all the endings!

Q: Where can I find the Cheshire cat's room?
A: Near the mansion entrance, in a room where the floor is a circular plate (maybe a table?), with two grand staircases and a red rug leading to a door in the background, there's a crack in the floor near the east wall.

Q: Where can I find the「 White Watch 」?
A: You picked this up automatically when time got turned back in Ending #3, the game was kind of quiet about it, so don't feel bad about not knowing you had this in your inventory the whole time.

Q: How can I get the 「 Hat of Truth」?
A: You must first close all time rifts. Closing the last rift will reward you with the key to the Castle dungeon. Take that to the dungeon and head deep inside...

Q: How can I convince Dodo to leave?
A: After convincing Humpty to leave, you can suggest that Dodo go to Humpty's world.

Q: How can I convince Humpty to leave?
A: Pass a speech check with her.

Or maybe not quite accurate? Please leave a comment so it helps other people, thanks! I'm just going by what I did in my own play through.