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