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