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.
Use a water fountain.
Get a basketball into the hoop in Playground.
Complete a course with Buddy.
Lose Buddy to the lava.
Unlock a follower.
Complete a community map course.
Complete all courses and trials in Wholesale.
Complete all Pogo trials.
Complete all Tiny Toy trials.
Complete all pursuit courses.
Complete all courses and trials in Basement.
Complete all courses.
Unlock all courses in Basement.
Complete all courses and trials in Master Class.
Unlock all courses in Master Class.
Jump 5000 Times.
Complete all courses and trials in Playground.
Find the hidden fort in Wholesale.
Unlock all courses in Wholesale.
Unlock all courses in School.
Complete all courses and trials in School.
Pick up a knapsack and run with it.
Pick up a pair of scissors and run with it.
Complete all challenges for a single course.
Unlock all courses in Playground.
Die by Collision.
Complete all courses and trials in Tutorial.
Complete a Pogo trial.
Jump 1000 Times.
Complete a Tiny Toy trial.
Complete your first "pursuit" course.
Unlock all courses in Tutorial.
Tweak something in the Options menu.
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.