Here is the full list of all 18 Cogs achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Earn every star
Complete 50 Time Challenges
Complete 50 Move Challenges
Complete 50 levels in Inventor Mode
Earn triple-gold on all music levels
Earn triple-gold on all flying levels
Earn at least bronze Time and Move awards on all flying levels
Earn at least bronze Time and Move awards on all music levels
Earn 400 stars
Unlock every level in Inventor Mode
Earn 200 stars
Complete 10 Time Challenges
Complete 10 Move Challenges
Complete 10 levels in Inventor Mode
Earn 10 triple-gold awards
Earn 100 stars
Finish a level in Inventor Mode in 5 seconds or less
Earn your first triple-gold award