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