you cannot get a rank offline. only on the online feature. if you play offline it is either in story mode or with a friend.
yes
The Xbox has nothing to do with the ranking on Call Of Duty, thats the online game developers of COD (Infinity Ward) error.
no but i recomend buying an xbox 360 instead
yes
Yes, online and offline.
no
no, your online rank will only be deleted if you delete your xbox live/psn account.
Yes, ranking up only relates to xbox live and xbox live games, matches, and stats in Call Of Duty 4
Call of duty 2
yes but you need xbox live playstation network or internet for the PC its only 2 player offline
You can get all the standard weapon skins offline, but if you want to get the downloadable skins, for example the Benjamin or the Bacon skin, you can't. You have to purchase those separately on the Xbox LIVE Marketplace or the PSN Store.
2 Call of Duty titles have been released for the original Xbox. They are Call of Duty: Finest Hour and Call of Duty 2: Big Red One.8 Call of Duty titles have been released for the Xbox 360. They are Call of Duty Classic, Call of Duty 2, Call of Duty 3, Call of Duty 4: Modern Warfare, Call of Duty: World at War, Call of Duty: Modern Warfare 2, Call of Duty: Black Ops and Call of Duty: Modern Warfare 3.(This information is as of 18 September 2012)