EDIT: Apologies for how this thread is posted, the original megapost I intended had too large of a body to be posted.
There are a lot of puzzles to remember so I wanted to add a reference sheet for each one to help! In the Main Run Floor 1 is always correct, the same can be said for Floor 0 in Marathon Mode.
1 Bathroom
This one is a bit silly but you need to flush every single toilet a single time. Back away from the toilets and to the right when you first come out of the elevator - a wall has been removed and there will be a large pile of toilet paper and a number on the wall above them. That Number is your answer.
2 Bedroom + Upside Down Bedroom
A quick solution to the bedroom is to turn off the light switch to the right. This exposes a number on the wall where the bed is which is the answer to the room.
Confirmed only for the Upside Down Bedroom - You can glance at the toy blocks on the "floor". The amount of blocks matches the number on the wall.
3 Giant Room(Desk)
For this room you have to run to the photograph near the end of the Giant Desk and the answer will be pinned to the back of the frame.
4 Lobby/Printer Room
An easy room that takes too much time - Run behind the counter on either the left or right and interact with the button on the printer. It will print out the answer.
5 Telephone Hall
This room requires you to run until you hit a dead end for the room to change shape. Do so again and then again until you reach the ringing phone. The number blotched in Red is the answer. Interact with the phone to change the room back to normal to reach the elevator. Path - Turn left, Turn left. Leave Dead End. Go Right, upstairs, go right, hit dead end, run left around the corners until you reach the phone.
6 Elevator Room
This room puts you on a floor with 6 elevators. Step out of your elevator and face it. In this position, count from the left going right to see what position your elevator is in. The position your Elevator is in is the clue for this floor.
7 Office Floor
This room has 5 total spawns for Golden toys. The amount of toys found is the clue for this room. One spawns on the left wall under the table and another in the trash can. One spawns in a chair, one spawns on the floor between chairs and one spawns in a corner behind the plants.
8 Treasure Dungeon
This room has 5 total chests in it. The number of chests containing Gold Bars is the clue for this floor. Meaning if your number is a 2 and you found 3 chests of gold, you don't have the check the rest of the chests.
9 Fountain Room
This room has a large fountain in the center of the room. The walls will spawn boarded up windows. The amount of windows is the clue for this room.
10 Sarcophagus Room
Run past the sarcophagus in the center of the room and go through the archway in the back, Make your way upstairs and around to pull the lever and jump down to count the gold bars inside the now open Sarcophagus.
11 Space Room
On the top right of the room is a guide to which symbol matches which number. Compare your floor number to the guide and find your matching symbol on the six available canisters. If your symbol as !! around it - the Floor is Correct. If your Symbol does not have !! around it, the floor is wrong.
12 Sewer Room
The Pillar at the end of the walking path has a number guide on its back. Glance to see how high the water level is on the chart to find your clue for this room.
13 Elevator Shaft Room
Fall down the shaft and count the red lights that show on each wall. The number of red lights you pass is your clue.
14 Cave Floor
The clusters of crystals can spawn a purple crystal in them. Count the number of purple crystals in the cave for your clue
15 Hotel Hall Room
This room starts with a pair of double doors and a hall with doors on either side. The doors on the left are the main focus. Each door relates to a number in order of when you pass them (1,2,3,4,5) - the door the opens is the number for the floor. First door opens - 1, second door on the left opens - 2, etc etc.
16 Infinite Room
This room seems to stretch on forever to the left and right. The first room has a pair of plants against the wall. Counting that room and each room you walk through until you end up back at the start is your answer. If you find 2 more rooms besides the starting room, the answer is 3.
17 Library Room
Walking along the path until you hit the dead end and run back, go down the middle path to reach a book pedestal that has the number for the clue scribbled on it. Go back and take the right path to hit a dead end then backtrack to the elevator. (You can cut the corner on the dead ends to trigger the room change early without having to walk all the way into the dead end to save time)
18 Subway room
Looking out the window you can see a schedule. One of the available listings will say (#) Minutes. This is the clue for this floor.
19 Prison Room
Scratched onto the right side wall are a bunch of lines. The number of lines on the wall is your clue.
20 Hedge Maze Room
This room contains a bunch of spiral statues. Count the statues to get your clue.