Here is the full list of all 21 Rooms: The Unsolvable Puzzle achievements.
Escape the toymaker's mansion.
Earn 432 puzzle pieces.
Clear all underground levels in Mansion 4.
Clear all underground levels in Mansion 3.
Make the toymaker's dream come true.
Clear all levels in Mansion 4.
Earn 324 puzzle pieces.
Clear all levels in Mansion3.
Clear all underground levels in Mansion 2.
Earn 216 puzzle pieces.
Destroy as many puppets as you can.
Clear all levels in Mansion 2.
Don't worry about failing.
Earn 130 puzzle pieces.
Rotate rooms often.
Clear all underground levels in Mansion 1.
Move rooms often.
Earn 80 puzzle pieces.
Clear all levels in Mansion 1.
Use the lamp often.
Earn 30 puzzle pieces.