The answer is yes. It is very easy to unlock iPhone nowadays. Unlocking websites are everywhere, they are a great help. You can also watch tutorial in YouTube to unlock it by yourself.
You can visit apple.com or visit a local apple store for unlocked iPhone.
Unless its an iPhone then it would be no.
You can check to see if your iPhone is unlocked by inserting a SIM from a different service provider and try to make a call, if its successful. Your iPhone is unlocked.
eBay or Craigslist
yes. once an iphone is universally unlocked it will work.
Yes, you can now buy the iPhone 4S unlocked direct from the Apple website
There are several providers of unlocking services for iPhones - both on location in Orlando, but if you don't have an unlocked iPhone yet, you could check out unlocked iphones on www.unlockediphones.net.
600
No!
Yes
No it has to be unlocked
Yes, you need an unlocked & Jailbroken iPhone. Which isn't cheap.