Here is the full list of all 41 Hot Lava achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Complete one sticker set.
Complete all courses and trials in Master Class.
Complete all courses.
Unlock all courses in Master Class.
Complete all Pogo trials.
Complete all Tiny Toy trials.
Complete all courses and trials in Basement.
Complete all courses and trials in Wholesale.
Complete all pursuit courses.
Unlock all courses in School.
Complete all courses and trials in School.
Complete a course with Buddy.
Lose Buddy to the lava.
Find the hidden fort in Wholesale.
Unlock all courses in Wholesale.
Pick up a pair of scissors and run with it.
Pick up a knapsack and run with it.
Get a basketball into the hoop in Playground.
Unlock a follower.
Unlock all courses in Basement.
Jump 5000 Times.
Complete a community map course.
Complete all courses and trials in Playground.
Unlock all courses in Playground.
Complete all courses and trials in Tutorial.
Complete a Pogo trial.
Use a water fountain.
Complete a Tiny Toy trial.
Complete all challenges for a single course.
Jump 1000 Times.
Die by Collision.
Complete your first "pursuit" course.
Unlock all courses in Tutorial.
Complete a course with no deaths.
Perform a "late" jump right after leaving a ledge 77 times.
Complete the first course in Tutorial.
Unlock your first character.
Jump 100 times.
Build up boost to 5 m/s.
Tweak something in the Options menu.
Complete the Intro.