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