Here is the full list of all 14 GORB achievements.
You completed a level under par.
You have collected 50 stars.
You have collected 100 stars.
You have collected 200 stars.
You have collected 400 stars.
You have collected all stars.
You have collected all stars in World 1.
You have collected all stars in World 2.
You have collected all stars in World 3.
You have collected all stars in World 4.
You have collected all stars in World 5.
You have collected all stars in World 6.
You have collected all stars in World 7.
You have collected all stars and beaten the bonus world..