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