Here is the full list of all 23 Airscape - The Fall of Gravity achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Rescue 100 sea critters
Rescue Snakebird from Snakebird
Rescue Fish from Nuclear Throne
Find a hidden level
Beat a level with Blue
Beat a level with Purple
Collect all the timed orbs
Die 500 times
Rescue 50 sea critters
Die 100 times
Unlock a Containment Level
Beat a level with Green
Beat a level with Red
Beat the game in under 60 minutes!
Unlock the final zone
Beat The Fall of Gravity
Beat the Octosphere
101% the game
Rescue all the sea critters
Die 2500 times
Rescue the Shopkeeper from Crypt of the Necrodancer
Rescue Guac from Burrito Galaxy
Rescue Cactus, Holly, Lemon, and Coral from Assault Android Cactus