Do autistic people, as individuals, not have rules in their own head about how people should interact with them?

Autistic people generally have either far fewer than allistics or if they have some kind of social obsession potentially they have a whole world of rules of their own that even allistics will struggle with.

But yeah generally, in my own case: 1) Don't be irrationally or sadistically mean.

That's basically it. You can be irrational/strange around me and at most I'll be surprised due it being unexpected and my "mask software" wont have a response to load and I'll freeze up for a bit. You can even be mean if there is sufficient justification for it. Maybe I fucked up bad.

Now, "being mean" a fairly broad category and I have specific obsessive silos of topics I don't want broken, but that's on the basis of a "info hazard". Mainly: discussions of poop or story spoilers. But if someone ends up breaking those "Rules" I don't hold it against them because they could not have known that I have a severe aversion to both of those things, I just warn them and move on.

In social groups composed entirely of autistic people, would another set of norms emerge that could get someone in the group scolded if they broke them, just like in the rest of society?

Yes but they'd probably be documented, FAQ'd, etc. Autistic people would tell rule violators to RTFM.

When a NT person upsets an autistic person because they broke a norm they weren’t familiar with, wouldn’t they also feel bad and try to remember not to do that in the future?

If the autistic person got upset at the person for breaking a norm the allistic was unfamiliar with they'd be being unfair assuming there was no good reason for them to have known in the first place.

Some taboos exist for good reason and apply across the board. We don’t greet strangers by asking them how their genitals are feeling, for example (although that would be hilarious).

I unironically would be pretty comfortable in a society that did that. At worst I'd probably be confused by why this was the thing people asked about but if I encountered a society that did such and I learned that as a common greeting I'd settle in fine.