Can I glorify mass murder?
Sure go ahead and glorify mass murder. More than a few stories like that around here. It's sort of important to have a plot and such though with it, otherwise it just comes off like being a shitty edgelord story. (It's okay to be an edgelord, just be an entertaining one)
Be extremely racist and spread a copious amount of hate?
There's been more than a few people on here claiming they were going to make some SUPER DUPER HITLER SIMULATOR, but most of the time they don't follow through since they were just shitposting and soon disappear.
We did have one guy that wrote a story on here that turned out to be a white supremacist for realsies since it was later discovered that he had an account on Stormfront (and it wasn't for trolling purposes). When he was confronted about it, he tried to claim he wasn't when it would have just been more honest to say "Yeah I'm down with the 4th Reich"
In any case, his story itself wasn't actually about Nazis winning WW2 or anything really obviously race related. He'd written part of his novel in game format on here which was to do with running a militia after the bombs hit and it was quite frankly boring as shit. Not like he had remnants of the noble Ayran race fighting the mongrel races lead by Jews with orbital lasers or something.
Ended up getting taken down for low ratings and being unfun. (And the author was equally unfun, so he was shoved in the ovens eventually as well)
Honestly I've only ever seen one example of a real "racist CYOA" (Like real as in I got the impression it wasn't being racist just for purely offensive purposes) done semi well and it wasn't on this site, it was on Infinite Story. And the author of that story ended up taking it down for whatever reason.
It's never really seriously been attempted here though (Actual Nazis don't tend to be excessively creative), so it would be a case of having to "write it and see" thing. Crank the maturity rating to 7 and put an extra warning on it in the description.
Etc, Etc, Etc
Of course the only major thing you didn't really mention was THE PORN. That's really the only thing that's the limit. You can't just have a story with page after page of people inserting whatever into various orifices and then a bunch of bodily fluids come out.
However, this isn't to say you can't have sex in a story. Sex just can't be the sole purpose of the story. As for how graphic the sex scene can be, well that's mildly more flexible though much like the human body, there's still limits. Obviously if you're just doing stuff like "fade to black" you're not going to run into any issues though.
Again it's a "write it and see" thing. Crank up the maturity to 7 and put an extra warning in description.
We're also not trying to attract the weird fetish crowds either, so unless you're mocking furries, vore fuckers, diaper shitheads and other degenerates in the story, for fuck's sake do NOT write anything involving weird fetish shit. (It's just one of the many reasons Warrior Cat fanfic was outright banned around here) And it probably goes without saying definitely don't glorify pedo shit.
This is a family friendly site after all, not a place for degenerates. (Even though they come here anyway)