I got all the upgrades, evolved my void twice, and got all the skills that weren't grayed out. Then I prestiged.
1) I don't know what prestiging did for me?
2) Prestiging reset all my upgrades EXCEPT automation. Those were still maxed out.
3) I could not start the Gravity Discipline challenge. Pressing the button would reset my upgrades (except automation) and leave my money the same, but nothing else would happen, and no challenge I could tell. I got to the $75,000 goal, and still nothing happened. I tried this multiple times.