Here is the full list of all 24 Cosmonious High achievements.
Reach the school. On fire.
Reach the Grand Hall
Extinguish All Fires
Enter Principal Glob's Office
Kiss a Bleb
Teleport through the portals in the collider
Drink fluid from your hand
Make Sunspot poop edible and eat it
Create a 6+ bleb conga line
Throw something through every hoop
Yeet World Ender
Repair all crystal connections in the school
Sing all 5 songs in Auditoriology
Stretch with the class in Sports Dome
Create every fluid with the Alchemizer
Complete the yearbook
Complete Honk's Story
Complete Blort's Story
Unlock all Prismi Powers
Beat the game
Collect all Pirates of the Gooniverse cards
Collect all Blebs
Fix everything wrong with the school
Ace the Game (Get every credit)