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.
Find the hidden fort in Wholesale.
Complete all courses and trials in Wholesale.
Complete all Tiny Toy trials.
Complete all Pogo trials.
Complete all pursuit courses.
Complete all courses.
Unlock all courses in Wholesale.
Complete all courses and trials in Master Class.
Unlock all courses in Master Class.
Pick up a pair of scissors and run with it.
Use a water fountain.
Get a basketball into the hoop in Playground.
Complete a community map course.
Complete all courses and trials in Playground.
Unlock all courses in Playground.
Unlock a follower.
Complete all courses and trials in School.
Unlock all courses in School.
Pick up a knapsack and run with it.
Jump 5000 Times.
Complete the first course in Tutorial.
Jump 100 times.
Jump 1000 Times.
Perform a "late" jump right after leaving a ledge 77 times.
Complete a course with Buddy.
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 Tutorial.
Complete all courses and trials in Tutorial.
Unlock all courses in Basement.
Complete all courses and trials in Basement.
Tweak something in the Options menu.
Die by Collision.
Lose Buddy to the lava.
Complete the Intro.