Here is the full list of all 12 Melody's Escape 2 achievements.
Finish your first track
Score at least 3 hearts in any difficulty
Perform a slow-motion jump
Score 5 hearts on a track in any difficulty
Get a Perfect Chain Score in any difficulty
Get a perfect Chain Score in Intense difficulty
Get a Perfect Chain Score in Intense difficulty 10 times
Play 10 tracks
Play 100 tracks
Play 500 tracks
Get a Perfect Chain Score in Intense difficulty 100 times