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