Here is the full list of all 10 Longboard Stunts and Tricks achievements.
Unlock all longboards
Complete the time-limited race on stage 1 in 55 sec or less
Achieve level 5 with any character
Cover the distance of 2000 m total
Complete all stages
Hit your rival 80 times during the race
Collide with 50 cars
Collect 20 speed boosters
Get off track 8 times
Complete the time-limited race on stage 5 in 38 sec or less