Thanks in advance for your expertise since I have very little experience with upgrades.

I'm booked in November ORD-LHR-BLQ business class and return premium economy. I booked on the AA website using AA flight numbers but the flights are on BA metal. I called AA reservations to see if I could use miles to upgrade (or at least get on a waiting list). I was told that this is not possible for codeshare flights. Did I make a mistake by not booking with BA and attempting a partner miles upgrade? I wish they'd be more clear about this on the website.

Question two: Since I'm in Club World can I use the BA lounge in T5 at ORD even though it's an AA ticket?

Thanks again.