AD backups using GRT feature

Ours is a Linux master (redhat 6 VM) and Linux media servers(appliance 5220) and we are planning to take Active directory backups using GRT.

Can you confirm the following ?

GRT requirements :

Domain Admin account -- Is it compulsory ? Local system account won't work ?
same version of NetBackup on all machines -- Is it compulsory ?
NFS should be enabled on all NetBackup hosts and enable client for nfs on client machine-- for linux media server we need not do anything ??
port requirements-- which ports to be opened and on which netbackup hosts ?