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.
101% the game
Beat the Octosphere
Rescue all the sea critters
Die 2500 times
Beat a level with Red
Rescue Cactus, Holly, Lemon, and Coral from Assault Android Cactus
Beat The Fall of Gravity
Beat the game in under 60 minutes!
Rescue 100 sea critters
Unlock the final zone
Beat a level with Green
Rescue the Shopkeeper from Crypt of the Necrodancer
Rescue Snakebird from Snakebird
Collect all the timed orbs
Die 500 times
Rescue 50 sea critters
Beat a level with Blue
Rescue Guac from Burrito Galaxy
Rescue Fish from Nuclear Throne
Beat a level with Purple
Find a hidden level
Unlock a Containment Level
Die 100 times