Probably not, they have different exterior shapes.
You can go to eBay!
yes they do they have the same design.
Probably not, it could work vice versa, but a #GS is too thick to fit in most iPhone 4 cases.
First of all, it's the 2g and the 3gs you are referring to. And I don't think so since the original 2g has a different exterior design.
Yes
Yes it does.
No. The iPhone 3GS is sadly a GSM only phone, so it cannot function on Sprint (or Verizon's) bandwidths.
I tried it with my 3GS and it does work.
iPhone 3gs
iPhone 3GS
No as the iPhone models have different shaped housing, so they will not fit earlier protective cases.
NO, the iPhone 3GS and 4 are differently shaped.