Thanks. Luckily customer service was able to change it which was better option than losing seats (now a different matter that someone additional from E+ getting upgraded to first, might free up better E+ ones, so might have to use the option you suggested).

Wondering if one has boarded last partner flight and only UA is left (all on same ticket), shouldnt one be already checked in for united as well. Or it’s only with certain partner airlines who can checkin on united and give BPs for united as well.