Hi, Thank you
1. you can treat different windows of inprivate mode the same way you treat a private window and a normal window, they can't exchange tabs. every new window will have their own cookies and session and moving tabs between inprivate windows won't be possible.
2. if a inprivate tab docs and gets removed from its parent window, it can return to the same window again no problem, but only to that window, not other inprivate windows. again just like you can't attach an inprivate tab to a normal tab in the same window, different inprivate windows will have the same rules applied to them.
honestly i don't think Microsoft has any shortage of engineers and they are more than capable :)
after all it's these differences that make the new Edge different than google chrome, by removing such barriers and limitations in the chromium engine, Edge will become a great browser.