
Samsung Galaxy S2 LTE (DoCoMo)
Every official firmware build for SC-03D, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/SC03DOMMY2

SC-02D

SC-02B

SC-01E

SC-01D

SC-01C
You can find the firmware on the model: SC-03D page.
Yes, all firmware files for SC-03D are 100% official, original, and obtained directly from Samsung servers.
To flash SC-03D, 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 SC-03D.