If the container is air tight then no reaction will occur with the absence of O2
Well, this is true, though the majority of octane loss is typically due to the lighter volatiles (responsible for octane level) evaporating faster than the heavy ones.
Yes, this is still mitigated by a well sealed container.
Oxidization accounts for only a small percentage of loss but can the oxygenates that are already additives in the fuel cause continuing oxidization even in a sealed container?
From what I'm reading, some degree of octane degradation occurs with age regardless of the storage conditions, though it can be slowed down significantly with proper care.
Why I don't know and I can't find any numbers indicating specifically how long or how much.
Might not be a big deal, but I've yet to see a straight answer on this from a source I'd trust.
Fuel threads can be a lot like oil threads, lol.
Bill