All right it seems that there is a lot written and probably I am not able to find it.
I am starting with my device model:
Version: PDA i900DXHJ1 /DXHJ1
Phone: i900DXHJ1
Bluetooth 2.0 + EDR
Wifi: IEEE 802.11 b/g
So my worries are

:
1. Can I create a back up (restore image) of my current phone installation (in case I want to go back to something original that I had)
2. How can I upgrade to official WM6.5 since on the official samsung update software my country is not enlisted (Bulgaria is my country). Can I use other country selection? Which one?
3. Is the flashing process with WM6.5 the same as with any other rom?
4. If I can not get the official 6.5 where can i see clean 6.5 rom?
5. What is the difference between flashing the PDA part and the PHONE part
6. Recommend good working ROMS (looking for fast performance, fast internet, fast GPS and good battery)
Thank you all in advance