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