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