7. Pop up window says "Application is still running. Force it to quit?" with a "Force Quit" button and a "Keep Running" button.
7.1. ????????????? WHY YOU NO CLOSED!?
Your application has terminated. The stub program that Qt Creator has run along with your program in order to connect its output with the Windows console window and wait for a key press is still running... it is waiting for you to "Press <RETURN> to close this window...". The process is called qtcreator_stub_process.exe (or the like) and is prominently visible in the console window title bar and task manager.

On my Windows XP box with an ancient Creator the stub process closes cleanly when you press Return. It may be a quirk of your OS version or Creator version that causes it to hang rather than close. In any case, it should not have any negative effect on your application which is long since terminated.

If your program does not require user console input then running without the console window is a viable option: output is visible in the "Application Output" pane in Creator.