Hello, I will allow my self to fulfil your request.
1. Just "Clone rendered frame window" (the max icon in VFB) there you can zoom in.
2. Im guessing you want to "make pause", change a fiew things and "unpause"?
That would require re/render of the scene anyway, so the only benefit would be gething your memory cluged especialy that IR is quite fast and responsive anyway.
3. Nbr? You mean number? There is a setting for that. Render Setup > Performance > Performance Settings > Interactive Rendering: Max Passes.
Id suggest contacting Adam Hotovy to talk about your payment plan, have a nice day.