https://portal.staralliance.com/cms/...1201b.pdf/view


Reference Guide - Reservations & Ticketing - Ticketing


Not totally related, but fyi
Irrops, intl flight + *G = they must provide certain amenities
Reference Guide - Airports Information - Irregular Operations Handling




These are all *alliance rules/guidelines. I doubt any Frontline employees will know about them, you have to escalate. For the irrop amenities, it should be simple to request reimbursement afterwards. For OP's case, harder to claim compensation after the fact (you already flew), best case to refund miles (good luck getting UA to tell AC to reimburse)