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