Throughout FNAMTB's development, there were a total of three mechanics introduced. This page will detail about them all.
There are a total of three extra choices in the game, two in Chapter 2 and one in Chapter 3, these didn't change how the story would go but it did change for what you would achieve at the very end of the game, after each ending you get one secret cutscene for everyone you got right (learn more on the "Extras" page).
This was introduced in Chapter 2 and you had to memorize the paths, or just create another save file, and in Chapter 3, you used your memory, with optional help from said save file. This was only used once.
Introduced in Chapter 3, this was a health system, three hits, you die. There were two instances this was used in. It appears as a heart at the top of the screen.