Here is the full list of all 19 Lily's Day Off achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
See ending 5 in the game
See ending 4 in the game
See ending 6 in the game
See ending 3 in the game
See ending 10 in the game
See ending 7 in the game
See ending 1 in the game
See ending 14 in the game
See ending 11 in the game
See ending 12 in the game
See ending 2 in the game
Find the secret menu!
Change Lily's clothes
See the game's true ending
See ending 15 in the game
See ending 8 in the game
See ending 13 in the game
Check out the game's credits
See ending 9 in the game