Here is the full list of all 25 Manifold Garden achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Grow a World
Complete the Blue Level
Collapse the Dark World
Enter the Dark World
Activate a Laser Beam
Fall from a Great Height
Earn Every Achievement
Shrink Down Into a Small Model of a Level
Grow a Tree
Grow a Double Gravity Tree
Power on a Water Wheel
Use a Hidden Path to Return to an Earlier Level
Solve a Puzzle Involving Portals
Change the Color of a Cube
Redirect Water Using a Cube
Redirect Water Through a Portal
Complete the Red Level
Complete the Yellow Level
Complete the Orange Level
Complete the Purple Level
Complete the Green Level
Complete the Rainbow Level
Open the Final Door
See the Ending
Complete the Game Without Placing a Single God Cube