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