How to repair an Iphone purchased in another country ?

Phones are different from computers. The current "repair" process is to replace the broken iPhone with a working one. Because there are technical differences for phones in different countries, to be able to "repair" iPhones from different countries, each store would have to stock versions from those other countries, a logistical nightmare, not to mention prohibitively expensive. So, for iPhone repairs, you need to return the phone to the country of purchase.

Yes, to date any repair required for the iPhone was what is referred to as "whole unit replacement". With that process, to "repair" an iPhone purchased in China, a store in Dallas would have to have a Chinese spec iPhone on the shelf. Or a British, Italian, German, Australian, Japanese, etc. How many iPhones just sitting on the shelf, just in case someone shows up with a broken iPhone from another country. A logistical nightmare, not to mention the expense of having thousands of iPhones setting on the shelves of stores around the world. Not my choice of support, but that's what we have.

Why was it done this way? I don't know, Apple hasn't said. Maybe to ensure the customer got a phone that had been repaired and tested. Maybe because it was faster for the customer to give the store a broken phone and get a working one back in a couple of minutes. Who knows, but that's the way it has been. I say "has been" because there have been rumors that may change and they may do some repairs in store, like maybe the back cover. How accurate are those rumors? Your guess is as good as mine. But until Apple changes, we are stuck with what we have.

It is easier for Apple to replace the phone than to order or stock parts for diffrent phones. It is what it is, and no amount of complaining here will change the reality that you will not be able to get it serviced in China.

Couldn't agree more but those are the rules for iPhone serviceing and repairs. It can only be done in the country where it was purchased. It may well be a security issue, but what, I can't imagine.

In any event, damage caused by yourself is not covered by any warranty and you may only be offered a replacement under the exchange scheme for which you will receive a refurbished item. The replacement will however carry a warranty but the cost will be significant.