Here is the full list of all 12 Castle of Illusion achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Found all the Magic Diamonds
Bounced on 7 enemies in a row without touching the ground
Completed all Castle Statues
Collected all of Donald's Chili Peppers
Completed a stage in Time Attack mode
Completed the Game
Broke the illusion of 25 enemies with projectiles
Found 50% of all Magic Diamonds
Collected all the Magic Playing Cards
Completed a Castle Statue
Broke the illusion of 75 enemies
Collected 50 Diamonds to unlock your first Painting in the Castle