No
Since the Nexus S, Google brought out the Galaxy Nexus, Nexus 4, and Nexus 5.
The Google Nexus S is from T-Mobile and Sprint.
There is not a product from Google which is named 'Google I' There are however products such as Google TV, Nexus One, Nexus S, Galaxy Nexus, Chromebook and also Chromebox.
There are only a few differences between a Nexus S and a Nexus S 4G. Nexus S is T-Mobile phone, while the Nexus S 4G is a product of Sprint's Samsung. The only other major difference is that the 4G version offers Google Voice.
Those two components are not interchangeable, not to mention that the Galaxy S2 has a much larger screen.
Yes, most phones these days come with a web cam. The Nexus S has a Front-facing: VGA (640x480)
You can find the Nexus static wallpapers if you do an image search. If you're looking for the Nexus live wallpapers, you can find those in the Google Play store.
There likely are hard cases with a holster for the Nexus S. You can search for it at a number of online retailers (Amazon, ShopAndroid, Cellular Outfitters, etc.).
It's unlikely. If and when the Nexus 5 comes out, the remaining supplies of Nexus 4's will be sold out to make way for the next generation device.
According to CNET reviews, the Samsung Nexus S does have a good video component, display screen, clarity for recording, and video playback. The service provider is AT&T.
Phone numbers for the most part are still preserved in the Nexus S' SIM card, as well as by Google. You can sign into your Gmail account, and look under Contacts on a desktop. As for pictures, if the Nexus S can still power on, you can connect it via USB to your desktop, and if you have the appropriate drivers downloaded, it should be able to read the folders in your phone. Look for the folder "DCIM", and from there, you can copy and transfer any images or video you may have.
I don't believe so. You can download Swype keyboard from the Google Play store.