Here is the full list of all 30 Escape the Backrooms achievements.
Beat the game with 4 players in Nightmare difficulty.
Beat the game in Multiplayer with Normal difficulty.
Beat the game in Easy difficulty.
Survive in Level 0 for 10 minutes in Singleplayer.
Find the exit in Level 55.1 in Singleplayer.
Find the exit in Level 52 in Singleplayer.
Find the exit in Level !~! in Singleplayer.
Find the exit in the Snackrooms in Singleplayer.
Find the exit in Level 0.2 in Singleplayer.
Find the exit in Level 3999 in Singleplayer.
Find the exit in Level 10 in Singleplayer.
Find the exit in Level 9 in Singleplayer.
Find the exit in Level 188 in Singleplayer.
Find the exit in the Cave System in Singleplayer.
Find the exit in Thalassophobia.
Find the exit in Lights Out.
Find the exit in Level 94.
Find the exit in Level 922 in Singleplayer.
Escape The End in Singleplayer.
Escape Level Run For Your Life! in Singleplayer.
Find the exit in the Poolrooms in Singleplayer.
Escape Level Fun in Singleplayer.
Find the exit in the Terror Hotel.
Find the exit in the Abandoned Office.
Find the exit in the Electrical Station.
Find the exit door in Pipe Dreams in Singleplayer.
Enter the hub and activate the outpost power.
Find the exit in the Habitable Zone in Singleplayer.
Complete Level 0 in Singleplayer.