Here is the full list of all 20 Diamond Joyce and the Secrets of Crystal Cave achievements.
Finish first level!
Finish tutorial scenario
Finish 20 levels
Finish 50 levels
Finish 100 levels
Killed by a monster!
Collect 25 diamonds
Collect 100 diamonds
Finish 200 levels
1 monster killed
25 monsters killed
Finish 2nd scenario
Finish 3rd scenario
Finish 4th scenario
Finish 5th scenario
Finish 6th scenario
Finish 7th scenario
Finish 8th scenario
Finish 9th scenario
Finish 10th scenario