Since the Nexus S, Google brought out the Galaxy Nexus, Nexus 4, and Nexus 5.
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.
Nexus S was created on 2010-12-16.
It never did, but it did get the Galaxy Nexus, which had a number of improvements over the Nexus S.
The Nexus S 4G is a CDMA phone and the Nexus S is a GSM Phone. This is the basic difference between these two phones. Most of the remaining configurations are same.
The Google Nexus S is from T-Mobile and Sprint.
The Nexus S is going for about $450. $200 with a two year contract.
The Nexus S came in both CDMA and GSM variants.
The Nexus S is no longer manufactured. The newest Nexus phones can be bought and used on the Sprint network.
You should be able to find an unlocked version of the Nexus S (GSM) that can work at most of the network operators in India.
If you can manage to get an unlocked GSM version, that could be possible. I believe that for a brief period, AT&T did carry a Nexus S.
It was manufactured by Samsung.