Here is the full list of all 15 Formless Adventure achievements.
Collect all coins on a level.
Complete a level in 60 seconds.
Complete a level in 40 seconds.
Complete a level in 30 seconds.
Pass the forest.
Pass the jungle.
Pass the underwater section.
Pass the eternal frost.
Pass a level without dying.
Die from thorns.
Die from needles.
Blow up some dynamite.
Die from lasers.
Buy the first accessory.
Climb to the top in the 17th level.