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