A bit late but here is your answer:

- For Endure you must play a complete world in one sitting. I suggest world 1 since it is the easiest. But take some time and patience with you
- For Missstep you need to "complete" the game first. Because there is only one possibility to get the Game Over Screen and it is in the last level of the game. You'll see it if you are there

for endure on easy counts? i did it on easy and it didn't gave me the achievement.