1. OP had a Y ticket, sat in Y and got Y amenities. If there was a policy regarding this on either pmUA or pmCO, it was that you get what you paid for. Since the merger, people have tried to ascribe the fact that they got an exception from one pm or the other and that therefore such was policy.

2. Movement between cabins is prohibited by UA's safety & security policy. Thus, any decision to permit someone to move between cabins is solely in the crew's discretion. If you ask what the policy is, it is that you sit where you are ticketed.

3. Same thing for free drinks. The way to "send" a drink is to pull out a CC and ask the FA to have the card run through and the drink delivered. If you do that, you may find that the FA waives you off and comps the drink.