This is correct. Link aggregation is handled by intelligent switches (see LACP). In this sense, a pair of 7731 is just one link between two switches.
I would be more concerned about interference between the two pairs. Even when you choose lowest and...
Not that I know of. You can re-print a guestpass that you created before, but this is rather hidden in the guestpass generation process. When generating a guestpass, I adopted it as a habit to copy the key to the comment field. This way, the keys (co...