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