Factory reset and clear cache will delete your apps, settings, sms and your contacts, so you need to back up.
This can be done via Kies (Kies air if you find connecting to Kies via USB difficult)
Or, with Contacts, it is better to save them in your Gmail account and then simply sync back to your phone (this will be done automatically)
It is useful to root your phone for more backup options: See this video :
http://www.youtube.com/watch?v=1h0HEgOlCak
The code you mention is not necessary, especially if you do not intend to update your phone using Kies.
What it does is to set your sales code to the geographic location you are in.
Regarding your S2 made in China ..... I was not aware that Samsung gave licences to China, but that wouldn't stop them from copying the process.
Does the 'made in China' phone have the same specification?
You could install an app like quadrant standard ' to check the specification and performance:
https://play.google.com/store/apps/d...standard&hl=en
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