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