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