Here is the full list of all 12 Jet Car Stunts achievements.
Complete all Puzzle levels.
Beat your own ghost in Time Trial level where you already have gold medal.
Get a bronze medal.
Get a silver medal.
Get a gold medal.
Complete Platforming Hard A under 0:50:00 with no retries.
Beat the time of 1:48:00 in Time Trial Easy A.
Beat the time of 2:26:00 in Time Trial Intermediate C.
Beat the time of 4:25:00 in Time Trial Hard B.
Complete all Time Trials.
Complete all Platforming levels.
Complete Platforming Impossible A without Retries.