The Chinese Apple store will not ship to Turkey.
Your warranty will only be valid in China. You would have
to return the iPhone personally to China or to friend/relative
in China for repair/replacement. Apple does not accept
international shipments for repair.
Some Chinese wireless networks use proprietary
bandwidths/frequencies/protocols. Are these the
same that your Turkish wireless provider uses?
Buy your iPhone locally to avoid these problems.
The online Apple Store in China sells the iPhone 5 as unlocked as long as you get the WCDMA/GSM model intended for use with China Unicom. You would have to call the physical Apple Stores and ask if they also sell the iPhone 5 unlocked.
Again, though, be aware that you will get no service nor support for a Chinese iPhone in Turkey. As imobl said, you would have to take or send the iPhone back to China should it ever need service.