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