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