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