yes in the sense that both storage processors are working and serving data

for an individual LUN it is ALUA - meaning optiming optimized access for on one SP and non-optimized on the other.

For NAS a file NAS server and ist file systems is served from one SP - other SP can of course server different ones

SP will work in active-active mode with Vplex.

Witout VPlex, it work as active-passive.

per LUN no - per SP yes

SP's are active/active - meaning both are doing I/O - there is no "standby SP"

Only in the sales pitch.