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