Here is the full list of all 21 Lost Hope: Backrooms achievements.
Play in multiplayer with other player
Arrive at the Level 0
Complete Level 0
Arrive at the Level 2
Complete Level 2
Arrive at the Level FUN :)
Complete Level FUN :)
Arrive at the Level 974
Complete Level 974
Arrive at the Level 40
Complete Level 40
Find cassette Ex. 1
Find cassette Ex. 2
Find cassette Ex. 3
Find cassette Ex. 4
Find cassette Ex. 5
Be killed by the Entity
Arrive at the Level !
Complete Level !
Arrive at the Level 193
Complete main story