Usually they are, you have configure the router for G wireless networks.
Rather no than yes. It will work if the router is configured to work in the "G" mode.
Yes it is backwards compatible
Yes, if you connect them using a LAN cable.
It should be, just make sure that your router is configured to work with both G as well as N networks.
It depends on which wireless adapter you are using for your xbox. You should have G or N.
Yes, you can. Wireless N devices are reversely compatible with G networks.
Most 802.11n routers are backward compatible and will support 802.11g.
Yes, a wireless n adapter is backwards compatible with wireless g. Check the box you are buying and it will tell you if it is compatible with which wireless ranges.
Yes they are all backwards compatible. N to G to B. BUT, your N network will slow down to G speeds every time the G device connects unless you have a MIMO set up.
The same as with wireless G card and G router.
Yes, however, your internet speed will only be that of the G router which is comparably slower than that of an N router.