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