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