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