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