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