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.
Jump 1000 Times.
Complete your first "pursuit" course.
Complete all courses and trials in Tutorial.
Unlock all courses in Tutorial.
Complete a Tiny Toy trial.
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 a Pogo trial.
Complete the first course in Tutorial.
Unlock your first character.
Jump 100 times.
Die by Collision.
Complete the Intro.
Tweak something in the Options menu.
Jump 5000 Times.
Complete all pursuit courses.
Get a basketball into the hoop in Playground.
Complete all challenges for a single course.
Unlock all courses in Master Class.
Unlock all courses in Playground.
Complete all courses and trials in Playground.
Complete all courses and trials in School.
Unlock all courses in School.
Unlock all courses in Wholesale.
Complete all courses and trials in Wholesale.
Unlock all courses in Basement.
Complete all courses and trials in Basement.
Complete all courses.
Find the hidden fort in Wholesale.
Complete a community map course.
Unlock a follower.
Complete all Pogo trials.
Pick up a pair of scissors and run with it.
Pick up a knapsack and run with it.
Complete all Tiny Toy trials.
Complete one sticker set.
Use a water fountain.
Complete all courses and trials in Master Class.