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