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