
Samsung Galaxy S 2
The latest firmware for Samsung Galaxy S 2 (GT-I9108) is I9108ZMBMB3 with Jelly(Android Bean), released on March 1, 2013 for 1 region (CSC). Every official firmware build for GT-I9108, newest first: one row per build with all regions (CSC) that received it.
You can find the firmware on the model: GT-I9108 page.
Yes, all firmware files for GT-I9108 are 100% official, original, and obtained directly from Samsung servers.
To flash GT-I9108, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing GT-I9108.