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