Win10 updated from Win8 - does clean install loose product key?

1. Install Win10 directly from the usb flash I used to install my desktop? If so what happens with product key, can it be found and saved before I run down my laptop? Does it matter that I'm sharing an IP adress with the desktop = another (actually purchased) Win10?

Use this option. With Internet connection, if asked for product key, click on "Skip This Step" or "I don't have a product Key". Windows will be activated automatically.

If that laptop has a Windows 8 OEM embedded key, it will be detected and used automatically. You won't be asked for a key of asked to select Home or Pro. The matching version is installed automatically. If you did the free upgrade your PC is currently activated with a Digital License. That same License will be used this time around. The key that goes with it is a generic key that everybody that did the free upgrade has. This utility will show you what's what.
ShowKeyPlus
If you did the free upgrade from the factory installed OS you should be fine to clean install of Windows 10 and not worry about a key. Windows 10 install media will read and use Windows 8/8.1 and 10 OEM embedded keys. If at some point you upgraded from Home to Pro, and then did the free upgrade, that throws a little wrinkle into things. If that's the case post back and I'll elaborate more on what to do in that situation.