u need a micro-SIM for any of the 4-series. and Apple wants u in their ecosystem, with iTunes acct/credit card, etc. there are workarounds, but if u live in HK/Macau and have a card, this is the simplest (and IMO safest) way to go.
when u get into China/used phones/jailbreaking, it gets more complex. lots of info on the Net--pls read and inform yrself if yr jailbreaking iPhones or getting into Android. it's not terribly complex, and another setup may work better for u, but pls do some research. i'm not a telco expert.
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