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