1) Who knows? Can you describe your experience in FS9 without requiring us to take a degree in clairvoyance? Take into account many of us have never run FS9, and rest assured most of us have not spied on you while you were running any application on your personal computer.
2) No. You can acquire the base simulator on discs but not the complete scenery or the third party content. Just like in FS9 or Doom. Unless, of course, by "entirety" you actually mean "base simulator". In this case, check the webpage.
3) bells and whistles are nice. My cats enjoy them a lot. But to enjoy FlightGear completely you'll require plenty of RAM memory, a modern video card and some external hardware like a joystick.
(Seriously, man, you realize your message doesn't include any useful information to get any appropriate answer from us, do you?)