I just used the chat service on Apple's website to gather the following information about iPhone 5S, which I think is quite useful:
Oct 14, 2013; based in the USA
- The contract-free version from T-Mobile is for sale right now for
- This version is not factory unlocked, because it doesn't support CDMA
networks (like Verizon or Sprint). It will only work on a GSM network, and has to have a sim card.
- This contract free phone CAN be used internationally or with a different carrier in the US, and it DOES NOT need to be unlocked. Provided the phone supports your network of choice, "once it arrives to you, all you will need to do is take it to a different carrier, and they will change out the sim card for you."
- This reason this phone is advertised under the name "T-Mobile contract-free" is the fact that it comes with a T-Mobile sim card installed.
I understand these don't answer your questions, but for those in the US, this can be very helpful. At least for me, it helped clarify what phones will work on what networks and such.