Here is the full list of all 12 Alter World achievements.
Jump! Jump! Jump!...and again Jump!
Finish game with second ending
finish game with first ending
last death!
Complete 50 Levels
Complete 40 Levels
Complete 30 Levels
Meet developer!
Forever gone to Alter!
Brave enough? die 100 times!
Complete 20 Levels
Complete 10 Levels