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