Originally Posted by
fantomass
I can answer this part - yes, you can use your Gold benefits and credit to another FFP. Although sometimes it can be a bit of a hassle - a number of threads on the subject.
Your answer to the OP is partially wrong.
Some airlines won't allow cross-benefiting ( take advantage of the benefits of multiple FFP at the same time ), so it depends on the airline.
Some airlines won't let the OP to the lounge unless he credits his flight to his *G card; some airlines won't care. Same thing for other benefits such as extra baggage allowance, free premium seating, mileage upgrades, etc...