"Can there be more than one Primary on a Local Area Network?"
Sure. Other Primaries cannot control them, however (Primaries can only control Secondaries).
"Can the Primary role be changed to another desktop and then back to original desktop later?"
Yes, in-app, and through a demotion (deactivation) of a Primary to a Secondary and a promotion of a Secondary to a Primary (requiring activation).
Sean Drohan
Stardock Product Lifecycle Manager