The specifications can be found here.
The battery that comes with the i9001 is the EB575152LU. It is stronger than the EB575152VU that came with the i9000 (you can use these too):
Installed Firmware ROM
When you enter
*#1234# in the phone mode, it reveals information about the phone and the installed firmware ROM. This is what my phone showed when I bought it:
PDA: I9001XXKG3, PHONE: I9001XXKG3, CSC: I9001DBTKG1, Build Info: Mon Jul 25 15:15:05 KST 2011