I'm unsure if this will work for everyone else but I played a few levels and unlocked bonus level one by getting the key in a level. Bonus level one is level 36.
Upon completing this level (well I actually failed as I had 13 strokes lol) this achievement popped along with these achievements:
Ten-Spot
Explorer
Intrepid
Also after completing that 1 bonus level I am at 72% for completing all 15.
Appears the game is pretty buggy.