1) No third-person omniscient.
That's how I normally write, but so many people whined about it so much, I largely gave it up for following one viewpoint character or switching between just a few. Apparently it makes most people confused because they can't switch between different perspectives. I have no idea what that's like, so I hope I fake it tolerably well.
2) No prologues.
If I need one, I write one. Usually I don't. I have a handful of projects where I started with a lot of worldbuilding, not quite the same thing but serves a similar purpose. The only one I can think of off the top of my head where I wrote a real prologue is "Damask Speaks" which introduces the headmates and how they came to be.
3) Avoid infodumps.
I'm actually rather fond of these when framed well, for example as encyclopedia excerpts as chapter heads. And demifiction! I love demifiction. It is pure infodump.
4) Fantasy novels have to be series instead of standalones.
Anything can be a stand-alone or a series. In my crowdfunding work, it's usually up to the audience. Far more of the series exist because the audience picked them than because I did.
5) No portal fantasy.
Oh hell no. You can have my gatefic when you pry it from my cold, dead hands. I love reading it; I love writing it. Both my SF television series -- Schrodinger's Heroes and The Blueshift Troupers -- are different types of gatefic. There's a dab of it in Monster House, although it's not a major theme there. I've written more of it elsewhere, mostly as stand-alones. But I would be happy to do a fantasy series of this too.
6) No FTL.
Also fuck off territory. Partly because I love the stories, but also because I've seen how many times humans think things are "impossible" (flight, heavier-than-air flight, faster-than-sound flight...) that come true. I can write hard science fiction, I just get more ideas for sociological SF and occasionally science fantasy.
Consequently a majority of my SF has some kind of rapid transit, but they're all different. The hiveships in The Blueshift Troupers have a huge impact on human culture. Tripping into the Future uses time dilation as a weapon. My main SF universe went through a succession of methods from generation ships to sleeper ships to various kinds of FTL. My science fantasy setting has all different kinds together, including one alien species whose ships are pulled by subspace dragons. Why? Because it's cool.
7) Women can't write "hard" science fiction.
Obvious fallacy, easily disproven by a few seconds of searching for books.
8) Magic has to be just a minor part of a fantasy world.
Magic can be anything you want or need it to be in a story. Internal consistency is advisable unless you establish up front that your setting's magic is unpredictable. Plenty of things can be that way. (Remember how unpredictable gunpowder was before people realized that air has water in it? You knew if you got your powder in the creek then it wouldn't fire, but not why a muggy day had the same effect.) Also you can have as much or as little magic in a story as you please.
Hart's Farm started out mundane except for small hints, and the magical aspects only became obvious later on. The Origami Mage is wholly based on a conflict between two mages, so of course it has lots of magic. One God's Story of Mid-Life Crisis has a deep background of magic because the protagonist is a god, although not all the episodes involve magic. Sort Of Heroes has magic in the surrounding world, but the main characters aren't involved in a great deal of it.
9) No present tense.
You don't get to take whole parts of language away from writers. Use it when needed. In Polychrome Heroics, I customarily write Damask in present tense because that makes the plural perspective work better. Tripping into the Future is not just present tense but second person, meant to suck in the reader. Walking the Beat is lesbian romance; I think I use a lot of present tense there just to capture the characters better as they adapt to their changing lives.
10) No "unsympathetic" characters.
I would say, don't make your characters ALL unsympathetic or nobody will want to spend time with them. Don't make them so off-putting that people want to get away from them.
But it's great to have characters that people love to hate, ones that keep readers hooked in hopes of seeing them get kicked in the balls. Smart, capable villains make the heroes work for their dinner. On the other hoof, some villains are really sad-sacks and some "heroes" are kinda dicks.
I actually have hard time keeping villains as villains, though. Readers often root for them to be redeemed. Okay, we can do that, I love that storyline. But it does mean I have to keep minting new villains.
That means in order to anchor the far end of the spectrum, I have to specify that these characters are batshit crazy. So there are guys like the Mandible (who finally got his fool self killed) and Haboob (still kicking) who are unsympathetic because of how appalling their actions are, even if there's some background justification (Haboob's village was shot up by American soldiers and they nearly killed him too).
Stories tend to be more exciting with the whole range of human potential represented, from saintly to diabolical, with a majority of people somewhere in the middle.
The one unbreakable rule of writing I've found? Thou shalt not bore thy reader. Everything else is more like ... guidelines.