IOS – Will I be charged any fees to use iTunes Radio with the AT&T unlimited data plan

There have been hacks in the past to enable tethering, but in almost all cases, the carrier can tell what you are doing. I have even heard that people that tethered were individually contacted by AT&T to let them know that the tethering fee would be added if they wished to continue tethering and asked the customers to come in to chat if there were perhaps a misunderstanding.

You'll want to look for an unofficial AirPlay receiver app on the jailbreak side of things since Apple isn't even allowing these for solid commercial sound apps - let alone video apps.

Long term - let's hope enough people push for network neutrality in the US cellular space so that there is one tariff for data based on volume - not how you intend to use that data.

Not likely unless Verizon agrees to release that phone for another carrier. Have a look at this guide on identifying iPhone models:

• Identifying iPhone models

The iPhone 4 you have is model A1349 (that should be printed on the back of the device), and if so, it is a pure CDMA phone so you cannot connect it to a GSM carrier due to differing radio technology.

Even if you were to jailbreak it or get Verizon to unlock it, it's only going to work with another CDMA carrier.

So in the USA - you need to find a carrier with coverage in CDMA EV-DO Rev. A (800, 1900 MHz) and that's primarily Sprint and Verizon. Since there is no SIM card in this device, you might not need to get it unlocked, but that will be a dialog between you and your potential carrier if they can provide coverage to it at the same time as Verizon may have it registered as "their locked device"

Due to bilateral roaming agreements - each CDMA tower in the US can and does serve multiple carrier devices - so it's likely that Verizon could prevent you from using your device on a competing carrier until you fulfilled your contract or convinced them to release that device's status in the common database for cell phones.

There are well over 50 regional and national carriers providing CDMA coverage according to this wikipedia article so you might have considerable options in some regions of the US.

_{Nore some of the information is old due to consolidation. Your main bets are C Spire, Sprint and Verizon.}