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