If it's already locked on their network - yes. If it's on another carrier's network - no.
erm depends if its locked into a contract or not if it is be sure it is locked into the "3" network
Yes, you can use a Flight 2 SIM card in an iPhone 3G, provided the SIM card is compatible with the network frequencies supported by the iPhone. The iPhone 3G is unlocked or locked to a network that supports the SIM card. Ensure that the SIM card is properly activated and configured for use in the device.
yes
If your 3GS is locked, you can't insert a SIM card.
No, you cannot initiate a FaceTime call when the iPhone is locked. However, if someone calls you via FaceTime while your iPhone is locked, you can answer the call directly from the lock screen. Once you answer, the phone will unlock automatically, allowing you to use FaceTime.
No it has to be unlocked
NO
Yes, you can use a Straight Talk SIM card in an AT&T iPhone, provided the phone is unlocked or compatible with Straight Talk's network. Straight Talk uses AT&T's network, so AT&T phones typically work well with their SIM cards. Just ensure that the iPhone is not locked to a specific carrier and that it supports the necessary bands for Straight Talk's service.
If you bought an iPhone 5s from eBay and it is locked with a fingerprint lock, it will not be possible to unlock it if you do not have the Apple account.
How to unlock nokia C6 locked by bell canada
No, it is constantly being broken down and rebuilt.