Yes, you can install Windows or Linux through a USB drive on the ASRock B450M-HDV R4.0.
Yes, you can install Windows or Linux through a USB drive on the ASRock B450M-HDV R4.0.
You're asking about what "fresh out of the box" means. If it's about not needing updates, it really depends on your CPU model.
X570 works fine without updates for Ryzen 3000. B550 models might require updates. All B450 boards likely need an update.
ASRock has started sending boards with 3000 series BIOS support, so it should work. Just confirm it has the appropriate label.
Apologies, I didn't catch that. You seem confident about the board you picked then.