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