Here is the full list of all 21 Oliver's Adventures in the Fairyland achievements worth 1,000 gamerscore.
Escape the dungeon
Kill the second boss
Find all treasures
Save the thief
Kill the first boss
Save the knight
Throw the sword 100 times
Find the dagger
Find the underwater treasure
Find the diving mask
Kill 50 monsters
Dust, hair and 2 flies
Find the flashlight
Find the spiked boots
Destroy 5 walls with bomb
Save the princess
Find the bomb
Activate the statue
Do 72 jumps
Die by the spikes 3 times
Don't fall from edge for 30 seconds