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