1. close() in QWidget as Mdi subwindow.
I use QWidget as Mdi subwindow. When I call close() widgets disapear but mdi subwindow remain?! Please run attached example and from menu select "Window 2 (QWidget)". Then hit Escape key. I found workaround for this issue (and use in "Window3 (QWidget)").

2. activation previous Mdi subwindow
Please run attached example and from menu select:
Window1 (QMdiSubWindow)
Window3 (QWidget) // first time
Window3 (QWidget) // second time
Then please hit 3 times Escape. You will see that when second Window3 disapears Window1 is showed (!!!) instead first Window3. This is bug in my opinion.