Yes
Yes, it is! I just installed the iOS7 beta2 on my iphone 4s. It performs well on 4s. Actually, you can even install iOS7 on iphone4 and even 3GS. I heard the iOS7 is slow and stuck on iphone4 or earlier iphone edition. But it definitely works fine on 4s!
if all you have is apps, then 16 GB.
Yes but there are also paid apps so only get the free apps.
it depends. an iPhone may have an 8 gb, 16gb, 32gb and 64gb(iPhone 4s) models.
The iphone4 is not coming out on t-mobile.
the 4 and the 4s are.
There are more features but dont think its the iphone 5. The 4s has a better camera and more storage. It also surfs faster, and loads apps quicker than the iphone 4.
Apart from the colours and the different memories you can buy, yes they are the same.
Yes, they have almost exactly the same dimensions, but the 4S is a bit heavier.
Yes via the many apps available from the app store
There are a lot of sites that sell iphone 4S covers, in my opinion www.ebay.com. Iphone 4 and the iphone 4s are both same size, so you could get an Iphone 4 case too.
yes