How do you access the button at level 49? I've noticed top runs have it sitting there. How do you unlock it?

you need to have 1 completion them it appears at level 1 the speedrun settings where you can "reset cycles".

@HYP_blizz You must complete the entire obby at least once to unlock it. After you did that, go to Stage 1 and there will be a "Speedrun Settings" board. Turn on "Reset Cycles" and the button should be there.

complete the whole obby, then you unlock some settings that can make completing the obby quicker