How do I know that my laptop can boot from the USB stick?

Question is above, would like to put my PC with a USB stick and the MediaCreatonTool from Microsoft again

He can do that

In the BIOS you can set the order of succession, and there's also a function key when booting where you can select the USB as a "one-time boot"

Ok xD

Exactly, this should actually be any current PC. Have even 12 years old PCs here in the house that can.

For this, first of all, the whole files that Windows had previously delete it. Now you've probably already created a bootable stick. Normally he will boot automatically. If he does not do that then go to the BIOS also called uefi and change the boot priority so that the USB comes first and then the SSD on which you want Windows

You do not have to delete everything first. That's complete nonsense. You can also simply rewrite Windows and get the folder "Windows Old" with all old files.

What should you do even if you had a virus and the PC does not boot and you can't format it.

Know me with something like that. I'm also active in this area professionally.

Quite peacefully I can only speak from my experience.

Usually all devices of the last 10 years can:-)