First part seems to mean that YOU have to redeem the voucher. And it can only be used for upgrading people in your household account. I'm not 100% sure if you, the voucher holder, need to actually be on the booking. But my reading of the rule seems to suggest not. So you can likely redeem a GUF2 for your spouse and child. I've never had this issue as I have no household account and no one in my actual household (I'm a nightmare to live with).

Codeshare flights CAN be in the booking. You just can't upgrade them. As said above, you can ONLY upgrade 1.) BA operated AND coded flights and 2.) AA operated AND coded flights. You can't upgrade a BA operated AA coded flight. You can't upgrade an AA operated BA coded flight. I don't see any problem of there is a QF or CX flight on the booking; you just can't upgrade it. I've GUF'd AA and BA flights no problem, even if there was an AS flight in there somewhere.