Here is the full list of all 12 WonderCat Adventures achievements.
Defeat boss in Elemental Chambers
Defeat boss in Molten Core mines
Defeat boss in Toxic Pipes
Win level 3.3 in less than 20 seconds
Defeat boss in Clouds world
Defeat the boss in Old Crystal Mine
Get all crystals on World 1
Get all crystals on World 2
Get all crystals on World 3
Get all crystals on World 4
Get all crystals on World 5
Get all crystals !