2. There are two kinds of Apple mobile phones in America, one is contract machine, AT & amp； T and other operators sell mobile phones1since 99 yuan. This has an operator lock, and you must use the operator's card to use it. If you bring this Apple phone back to China, you can use the card to unlock it, but when upgrading the system, you need to upgrade the baseband, and iMessage and Facetime cannot be activated.
3. The other is Apple's bare metal, which can be bought in Apple stores in America. Bare metal is not limited. Moreover, iPhone6 supports the whole network version, and you can use Unicom's card. Since Unicom and Mobile were widely used in previous versions of Apple phones, another version was needed for telecommunications. At the time of 4G, all three operators adopted TD-LTE, so they can all support it now.
4. If the Apple mobile phone you bought is a contract machine, you can't upgrade or use all the functions of the Apple mobile phone in Chinese mainland, but the bare-metal Apple mobile phone you bought in the United States can be used in the mobile phone cards of three operators after being brought back to Chinese mainland.