Please forgive the rudimentary questions, as I tried looking online but the information on the Qatar website is not very clear. I just applied for and received gold status after obtaining the Cardless card.

1. When looking to upgrade a paid fare with avios or qcredits, should I look at it segment by segment, or by married segment? (E.g., if looking to upgrade a LAX - DOH - SIN)

2. I have a plethora of Alaska wallet funds, and they sell QR marketed and operated flights on the AS website.
A. Would these flights count toward the 4 segment minimum if I attach my QR FFN?
B. Could I use Qcredits or avios upgrades with these flights, space available?

3. I have an R marketed KUL - DOH - SFO flight. Can I buy up to the F lounge, and would they let me in the night before my flight to SFO?