Yes, unless it is "jailbroken" which is a violation of Apple's warranty. I wouldn't recommend jailbreaking it.
You can use the AT&T iPhone coupon code if you plan to purchase an iPhone. You can not use it if you plan to buy another phone.
you can tbuy an iphone without at&t.....
Yes, use your friends'.
In theory, yes. T-Mobile is actually the carrier for the iPhone in Germany. Keep in mind, however, that unlocking an iPhone completely voids its warranty, and if anything happens to it, the only recourse is to purchase a new iPhone. Apple will not service a broken iPhone if it is unlocked.
OF COURSE. That's why they say if u have at&t service you can buy the iphone there or if you have an ipod touch, you can go to at&t and they can help you develop it to a phone, like an iphone.
You will have to first get the phone unlocked.
Verizon, Sprint, and AT&T
Right now you can get the iPhone through AT&T and T-Mobile. All you do is order a sim card and you can use T-Mobile on your iPhone. WHen it will be able through other carriers some people say will be in January when the iPhone goes to Verizon, and October when it goes to Sprint.
You don't "have" AT&T, the iPhone comes with the ability to connect to AT&T.
Iphone 5.
Iphone 5
Yes the iPhone uses sim cards. Depending on the iPhone you want to put your sim in. If its the original - the 3gs yes but the iPhone 4 or 4s not. Side note, you may not get all services because you need to add a data plan.