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