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.
Pick up a pair of scissors and run with it.
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.
Unlock a follower.
Complete one sticker set.
Complete all courses and trials in Master Class.
Unlock all courses in Master Class.
Use a water fountain.
Complete all courses and trials in Wholesale.
Unlock all courses in Wholesale.
Complete a course with Buddy.
Lose Buddy to the lava.
Find the hidden fort in Wholesale.
Unlock all courses in School.
Complete all courses and trials in School.
Complete all courses and trials in Playground.
Unlock all courses in Playground.
Pick up a knapsack and run with it.
Jump 5000 Times.
Get a basketball into the hoop in Playground.
Complete all courses and trials in Tutorial.
Complete your first "pursuit" course.
Unlock all courses in Tutorial.
Complete a Tiny Toy trial.
Complete a Pogo trial.
Die by Collision.
Jump 1000 Times.
Complete all challenges for a single course.
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.