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