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