[Q] Samsung S6818-HELP:Upgrading and Change the device status topic

Hello, Everybody!

My English is so poor,Sorry!
I bought a Samsung Galaxy Fame (S6818:China Mobile Custom) last year.

It used:
ARM:SP8810 1.0GHz+Mail-300 RAM:512MB Screen:800*600 165ppi TFT
Android:4.1.2+TouchWiz Network:EDGE+GPRS+TD-SCDMA+(HSDPA/HSUPA)

Now I have rooted it several minutes ago.

You can Google "Samsung Galaxy Fame" for more information.(Model:S6810)

Then I go into the settings.It noticed me "Can't upgrade.Because your device is custom."
I found the device status,it changed from "Official" into "Custom" after I root it.

I have some Questions,Please help me.
These are my questions:
1.How to change from "Custom" into "Official"?(Of course,Root permissions must be reserved)
2.Can I update my system to Android 4.2+?
3.Can I upgrade to AOSP/CM?
4.Please give me an "Odin Download Link".
5.Who can tell me how to go into "Recovery Mode"?(Please give me all software in need.)
6.The latest system version is?
7.Can I change the connection from "MTP" to "Mass Storage Device"?

Thanks a lot,
Andrew Yang