
Samsung Gear S
The latest firmware for Samsung Gear S (SM-R750B) is R750BVJU2BPI1 with Android 2.2.1.3, released on August 30, 2016 for 1 region (CSC). Every official firmware build for SM-R750B, 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/R750BVJU2BPI1
All 10 builds in our database run Android 2.2.1.3. The newest build, R750BVJU2BPI1, was released on August 30, 2016. No new build has appeared for 123 months, so regular updates for this model have most likely ended.
Specifications of SM-R750, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-R750J

SM-R850N

SM-R765N

SM-R855F

SM-R640N
The newest firmware for SM-R750B runs Android 2.2.1.3: build R750BVJU2BPI1, released on August 30, 2016.
The latest build for SM-R750B, R750BVJU2BPI1, was released on August 30, 2016 (10 years ago).
SM-R750B has had no new firmware for 123 months, so regular updates have most likely ended.
Yes, all firmware files for SM-R750B are 100% official, original, and obtained directly from Samsung servers.
To flash SM-R750B, 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 SM-R750B.