Regarding #2 & #3: 32Gb FC is specified, so (unless you sell them an all SAN array) the multipathing will be ALUA. Each host will have paths to each node, and in a node or path failure, the host will retry failed I/O to alternate paths. The retry is at the driver level, so the application doesn't see it, only some additional latency for the (in theory one) I/O operation that experiences the failure. Subsequent I/O happens on the alternate path(s) until the node or path recovers. None is queued.
But these questions, along with the DC and DR notations, make me suspect that they are thinking of a pair of systems, as in a metrocluster.