Here is the full list of all 20 Melon Journey: Bittersweet Memories achievements.
Start Act I
Start Act II
Start Act III
Get normal ending
Lily quest complete
Thievery Snake quest complete
Vagabond Mouse quest complete
Mambo quest complete
Pup Star quest complete
Get secret ending
Accidentally deliver Antony to his home town
Count the bouncing ball to 100
Get postcard
Break out of jail
Return Darla's violin
Witness Percy's tragic fall
Get roller skates
Reunite Ocean Pup with his parents
Give Donny a bowl of chili
Save game with Bear Who Lost Everything