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 all courses and trials in Playground.
Unlock all courses in Playground.
Pick up a knapsack and run with it.
Jump 5000 Times.
Get a basketball into the hoop in Playground.
Complete a Pogo trial.
Complete all courses and trials in Tutorial.
Complete your first "pursuit" course.
Unlock all courses in Tutorial.
Jump 1000 Times.
Perform a "late" jump right after leaving a ledge 77 times.
Complete a Tiny Toy trial.
Complete all challenges for a single course.
Complete the Intro.
Complete the first course in Tutorial.
Jump 100 times.
Complete a course with no deaths.
Build up boost to 5 m/s.
Unlock your first character.
Tweak something in the Options menu.
Die by Collision.
Complete all pursuit courses.
Complete a course with Buddy.
Unlock all courses in Master Class.
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.
Complete all Tiny Toy trials.
Lose Buddy to the lava.
Complete one sticker set.
Use a water fountain.
Complete all courses and trials in Master Class.