Here is the full list of all 18 Grow Up achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Collect all crystals
Complete the game 100%
Complete all challenges
Orbit the entire planet in BALL mode
Unlock all Telerouters
Throw 100 seeds whilst gliding
Unlock all seeds
Discover the bull and the sheep
Ride two Sporchids simultaneously for 400m
Bounce on a Youch 7 times without touching the ground
Complete a challenge holding a Critter
Take a Critter to the moon
Discover letter block P
Rescue MOM
Flower all STARPLANTS
Visit all biomes
Plant 10 Champolines on top of each other
Blast a Critter 100m