On the Menu screen, click the Discord icon.

In the Chemical Room choose the left-most jar. See picture.

In the Chemical Room choose the center jar. See picture.

You will have to play this section twice. In the Chemical Room choose the jar all the way to the right. Make sure you take the gun, located all the way to the right of the screen/room.

To trigger the Predator achievement, go to the right edge of the sofa while making your way back. I'm not sure this is the only way to do it, but it's how it worked for me.

Items can be difficult to see at times in this game. Here are the locations of items you will need to progress the game.

Spraybottle: on the Lobby desk, to the right. Use it to clean 3 stains in the Lobby and 1 in the Utility room.

Trashbag: click the left-most door, the trashbag is on some boxes to the left. Use it to clean the pizza box on the desk in the Lobby, something on the floor (a banana peel?) near the Utility room door in the Lobby, the rusty cans (?) on a Lobby chair and more rusty cans (?) outside by the truck. Take the trash all the way to the right (past the Pool Room door) to the dumpster.

Keycard to Pool Room: on the left-most chair in the Lobby.

Chemical Room: Left-most door in the pool room. Gun is located all the way to the right on some boxes.

Other: Falling / jumping in the pool, while hilarious, will not result in an achievement or funny scene. The game will reset to right before you fell / jumped.