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.
Find the hidden fort in Wholesale.
Unlock a follower.
Complete all courses and trials in Wholesale.
Complete all courses and trials in Basement.
Complete a community map course.
Complete all Pogo trials.
Complete all Tiny Toy trials.
Complete all courses and trials in Master Class.
Complete all pursuit courses.
Unlock all courses in Master Class.
Complete all courses and trials in Tutorial.
Complete all courses and trials in Playground.
Unlock all courses in Basement.
Complete all courses.
Complete one sticker set.
Use a water fountain.
Unlock all courses in Wholesale.
Complete the first course in Tutorial.
Complete a course with Buddy.
Get a basketball into the hoop in Playground.
Unlock all courses in Tutorial.
Pick up a pair of scissors and run with it.
Pick up a knapsack and run with it.
Lose Buddy to the lava.
Jump 100 times.
Jump 1000 Times.
Jump 5000 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 Playground.
Complete all courses and trials in School.
Unlock all courses in School.
Tweak something in the Options menu.
Die by Collision.
Complete the Intro.