I'm planning a RTW that would include travel in both 2021 and 2022. I've read the threads on PQP limits for partner travel, but am not sure about how that would apply for a trip with a dozen segments across multiple carriers.

1. Is the Star Alliance site the only place to book (not somewhere on United)?
2. Can I see what the PQP will be before booking?
3. Does it get credited when I pay or as I take the flights (so there's a PQP per flight)? I think it's the latter, but my intuition about PQP isn't very solid yet.

What else do I need to consider? This would be in biz so I'd be hoping to get a big chunk toward 1K.

Thanks.