
Samsung Gear S (DoCoMo)
The latest firmware for Samsung Gear S (DoCoMo) (SM-R750D) is R750DOMU1BPA3 with Android 2.2.1.4, released on January 19, 2016 for 1 region (CSC). Every official firmware build for SM-R750D, 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/R750DOMU1BPA3
All 6 builds in our database run Android 2.2.1.4. The newest build, R750DOMU1BPA3, was released on January 19, 2016. No new build has appeared for 131 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-R540N

SM-R640N

SM-R630N

SM-R420N

SM-R530N

SM-R900N

SM-R910N

SM-R840N
The newest firmware for SM-R750D runs Android 2.2.1.4: build R750DOMU1BPA3, released on January 19, 2016.
The latest build for SM-R750D, R750DOMU1BPA3, was released on January 19, 2016 (10 years ago).
SM-R750D has had no new firmware for 131 months, so regular updates have most likely ended.
Yes, all firmware files for SM-R750D are 100% official, original, and obtained directly from Samsung servers.
To flash SM-R750D, 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-R750D.