A:Answer These are actually unrelated.
An unlocked phone can be used with multiple carriers, versus those coded to work with only one carrier. Note carriers will provide the unlock code, if you want to move from, say, T-Mobile to AT&T. And there are some differences with phone carrier technologies. For example, the same phone will not work on Verizon and AT&T.
You will need a Google account to download Android applications from the Google Play Store. It also opens up other backup, restore and integration features.