FNAF 1 MAP:
there's some stuff hidden behind some paintings

FNAF 2 MAP:

to proceed to the fnaf 3 map you need 4 crying children heads

1st: Located in the office behind a painting, you'll have to parkour and jump in the part where there is a moon

2nd: it's on the right vent in the part where there's water on the floor

3rd: it's on the Female's Bathroom under the mirror to the right there's a trapdoor, get in there and there's a whole room inside there covered with black blocks with a puppet hidden there

4th: on the carousel

Once you get all the heads you will need to go where the furnace are located and place each head on their respective furnace forming the code: 1 9 8 7

FNAF 3 MAP: there's numbers sperad out all over the map

1st: at the first exit close to the office behind the flames

2nd: at the left of the third arcade

3rd: hiding in one of the vents in the hall where bonnie is

4th: on the office's chair

once you find all these 4 numbers (not necessarily needed) you will have the numbers: 1 9 8 3
now go to the hall where puppet and chica are and jump in the painting

keep going until you find a bunch of furnaces again

open the chest and place the flowers forming the number: 1 9 8 3

FNAF 4 MAP:

There's an easter egg in the plushtrap hallway in the 2nd right door, inside that room if you go to the left you'll find the minigame house with the Fredbears Family Diner restaurant

To proceed to sister location go through the painting on the left hall and continue through the fire parkour

SISTER LOCATION MAP:

Go to the private room on the right room (Funtime Auditorium), inside that room go to the left and you'll find the private room
inside that room go to the left hall in the supply closet and hold shift to enter the cyan trapdoor then proceed through the vent

go to the bathroom of michael's house and interact with the lever at the left

then keep walking through the hall and when you find a door with levers enter the code: L E F T Y