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