Full Screen is what it says Full Screen. In Resurected Full Screen is Borderless Maximized window, that’s why you cannot change the resolution. On my IBM P77 i could have from 640x480 to 1920xx1440 and they were all fullscreen.
b) Really? When you want to play with lower resolution in a game, on higher resolution monitor its upscaling and it can be done by monitor even.
Edit:
Found another post on the forum why it is maximized borderless window: