
Samsung Galaxy Tab3 8.0
Every official firmware build for SM-T312, 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/T312JVUCOA2
Box codes of SM-T312 for different colors and markets. Firmware is chosen by the model code SM-T312 and your region (CSC), not by the SKU.

SM-T290N

SM-T537A

SM-T800X

SM-T807V

SM-T230X

SM-T230NY

SM-T237V

SM-T232
You can find the firmware on the model: SM-T312 page.
Yes, all firmware files for SM-T312 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-T312, 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-T312.