For point 1, consider a flash drive with only a USB-C connector on it. The kind of adapter that you'd need to plug that into a laptop with only USB-A ports is exactly the kind that the spec forbids.
My understanding is that they're "fine" if you only use them "correctly", and that the reason they're forbidden is that it's so easy to plug things into them in ways that will create a short circuit (e.g., plugging the C end of an A-to-C cable into one).
you don't need any adapter. all my USB-C drives come with a cable that has C on one end and A on the other. again, those cables are allowed. only adapters that would allow you to use a C-C cable may not be. so connecting a USB-C drive to an old laptop that only has USB-A plugs is fine, and is supported.
oh, ok, those seem to be rare though, and personally i find them impractical because the C connector makes them less stable. with an A connector the flash drive can be so small that it almost fits inside the connector entirely. in other words, buying a device that can't handle these flash drives would be a tradeoff that doesn't have much of a downside unless i already have such a drive that i really want to use.
but if i have a tendency to buy older devices, then i likely also have a tendency to avoid getting such modern drives. they will be coming though, thanks to USB4, and there will be a day where i can't avoid needing a laptop with at least two USB-C ports (because one of them will be used for charging), or get a USB4 rated USB-C only hub. and hopefully by then even older laptops will already have at least one USB-C port too (even if it doesn't support USB4 yet).