Does the arena have a machine to take cash and give a credit voucher towards sales since they take no cash

YES

They have reverse ATM that you put cash in and it gives you a debit. The debit card can be used in the arena and any where else outside I worked there and sure of it

Yes they do. I saw it on opening night.

Not that I know of. Credit cards. If you don't have 1 I would get a prepaid one.