Grass is used in the level editor to spice up the look of your level. You can cover the surfaces of polygons with grass. You can add grass automatically with ALE. When inserting grass manually, you have to make sure that the longest horizontal edge of that polygon is not in the side where the grass should be. If you didn't understand that, see Designing section.
Apples can affect the gravity in a level. You can set an apple to change gravity to down, up, left or right. Note that you can't get gravity off because without gravity you couldn't accelerate at all because there wouldn't be any grip. You should think twice before inserting a gravity apple, because not all players like gravity levels. You can usually design the level so that gravity apples are not needed. Though, when used lightly and in a correct way, they can make your level even better. You can usually find more gravity apples from a noob designer's lev than from an experienced designer's lev.
GAAs are given annually to best players/designers in that year. In each year there is a specific GAA jury which consist of 6 veteran kuskis who have been active in that year. The system goes so that first community can give their suggestions to jury. From those suggestions, jury collects 10 candidates to each category. After that community can vote for their best candidates. After that the winners are chosen in special gaa final show. The current categories in GAA are internalist, externalist, battler, rookie, designer, team, wr, style, replay, level, contest, contribution, achievement and site.