Here is the full list of all 19 Behind The Beyond achievements.
Play the game atleast once
Play the level -1 atleast once
Play the level -2 atleast once
Play the level -3 atleast once
Play the level -4 atleast once
Play the level -5 atleast once
Play the level -6 atleast once
Play the level -7 atleast once
Play the level -8 atleast once
Completed level - 1
Completed level - 2
Completed level - 3
Completed level - 4
Completed level - 5
Completed level - 6
Completed level - 7
Completed level - 8
Respawn atlest once
play all 8 levels and complete it