
The latest firmware for GT-B9150 is B9150UEUBNF1 with Jelly(Android Bean), released on July 30, 2014 for 1 region (CSC). Every official firmware build for GT-B9150, 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/B9150UEUBNF1
All 10 builds in our database run Android 4.2.2 (Jelly Bean). The newest build, B9150UEUBNF1, was released on July 30, 2014. No new build has appeared for 148 months, so regular updates for this model have most likely ended.

GT-B9120

GT-B9062

GT-B5512B

GT-B5512

GT-B5510L

GT-B5510

GT-B9388

GT-B5330L
The newest firmware for GT-B9150 runs Android 4.2.2 (Jelly Bean): build B9150UEUBNF1, released on July 30, 2014.
The latest build for GT-B9150, B9150UEUBNF1, was released on July 30, 2014 (12 years ago).
GT-B9150 has had no new firmware for 148 months, so regular updates have most likely ended.
Yes, all firmware files for GT-B9150 are 100% official, original, and obtained directly from Samsung servers.
To flash GT-B9150, 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-B9150.