Here is the full list of all 19 Race.a.bit achievements.
Upload a track you created.
Win bronze medals on all official tracks.
Win bronze medals on at least half of the official tracks.
Explode.
Rate twenty community tracks.
Race on ten community tracks.
Rate a community track.
Fall of the edge.
Rank in the top 10 of a highscore list.
Win a bronze medal on at least one official track.
Win gold medals on all official tracks.
Upload ten tracks you created.
Upload twenty tracks you created.
Beat a friend on a track you created.
Race on fifty community tracks.
Race on a hundred community tracks.
Rate fifty community tracks.
Challenge a friend.
Unlock all achievements.