1. I don't believe this is always enforced.
2. Award Nexus, KVS, AA.com
3. BA will not release all empty seats as awards to fill CW, there is no real way to predict if seats will become available other than monitor other dates on the same route and see if they open up, and what their loads are.

BA's upgrade system is very simple and transparent. If there is an award seat in the next class, and you are in an eligible fare, you can upgrade.
I don't believe AA immediately confirms upgrades, or that it is quite as obvious whether an upgrade will clear.