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