Only if the iphone is a GSM phone with a SIM card... Otherwise if it is CDMA then no, you have to activate the other iphone.
Im not sure but i think you have to jailbreak it
iTunes is not required to activate the 4 or 4s. Insert SIM and turn on and follow the prompts.
Apps and music will work, but you can'y call people without a wireless plan.
i've had both, and i will never have another phone after having the iphone.
Jailbroken and are not located in the US.
No. You can't activate the iPhone without activating service plan. If you are just looking for the ipod and internet functionality, you should consider the iPod touch
iCloud bypassing is the way to unlock the iPhone activation lock without the Apple ID. You can use this method when you do not know the Apple ID username and Password. The are many free and paid tools for activate the iCloud unlock. use a trusted tool for activate the iPhone lock.
Settings, General, Network
Yes, activation needs to be made through the internet.
activate the phone first and then sync it with your itunes on your computer
you dont
Yes, you can find your lost iPhone with an iPhone app. However, you must have access to another apple product with the same app to locate your lost iPhone. It's called FindmyiPhone in the app store, and it's free. All you do is make an account. Let's say your iPhone is lost, all you do is sign in with your account with another device with the same app and the app will do the rest. Its quite amazing.