
Samsung Galaxy Tab PRO 8.4 (3G)
The latest firmware for Samsung Galaxy Tab PRO 8.4 (3G) (SM-T321) is T321XXS1BQB2 with Android 4.4.2 (KitKat), released on February 13, 2017 for 3 regions (CSC). Every official firmware build for SM-T321, 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/T321XXS1BQB2
All 10 builds in our database run Android 4.4.2 (KitKat). The newest build, T321XXS1BQB2, was released on February 13, 2017. No new build has appeared for 118 months, so regular updates for this model have most likely ended.

SM-T290N

SM-T537A

SM-T800X

SM-T807V

SM-T230X

SM-T230NY

SM-T237V

SM-T232
The newest firmware for SM-T321 runs Android 4.4.2 (KitKat): build T321XXS1BQB2, released on February 13, 2017.
The latest build for SM-T321, T321XXS1BQB2, was released on February 13, 2017 (9 years ago).
SM-T321 has had no new firmware for 118 months, so regular updates have most likely ended.
Yes, all firmware files for SM-T321 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-T321, 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-T321.