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