QuickTime can already "do" Flash (.swf) and Flash Video (.flv).
The "trick" for some files is to revert the "Publish" state to Flash 5 (or lower) format. Most newer .swf files can't be opened because they were created as Flash 6 and higher. But they can be converted if you have the right tools.
Flash can be used just like any other track. It can be used for movie controllers or buttons for links.
They lose the audio if exported (just like any other muxed track file).
Yes. If the .swf file was published as Flash 5 or lower.
Trouble is that a viewer can't "see" the publish state of a Flash file so it takes some trial and error.
Find an "old" .swf file and Control-click Open With QuickTime Player.
To "convert" newer .swf files you'll need the Flash application.