Here is the full list of all 9 Cat Quest II achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Completed all 67 side quests!
Obtained all 101 equipment!
Reached level 99!
Cleared all 73 dungeons!
Obtained all 12 spells!
Completed the Main Quest!
Unlocked 3 Royal Arts!
Entered the new continent!
Completed the first quest!