
Samsung Galaxy A8
The latest firmware for Samsung Galaxy A8 (SM-A800YZ) is A800YZZTU1BPL2 with Android 6.0.1 (Marshmallow), released on December 13, 2016 for 1 region (CSC). Every official firmware build for SM-A800YZ, 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/A800YZZTU1BPL2
SM-A800YZ started on Android 5 and has received 1 major Android upgrade; it now runs Android 6.0.1 (Marshmallow). The newest build, A800YZZTU1BPL2, was released on December 13, 2016. No new build has appeared for 120 months, so regular updates for this model have most likely ended.
Specifications of SM-A800, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-A800X

SM-A805N

SM-A700X

SM-A810F

SM-A908N
The newest firmware for SM-A800YZ runs Android 6.0.1 (Marshmallow): build A800YZZTU1BPL2, released on December 13, 2016.
The latest build for SM-A800YZ, A800YZZTU1BPL2, was released on December 13, 2016 (9 years ago).
SM-A800YZ has had no new firmware for 120 months, so regular updates have most likely ended.
Yes, all firmware files for SM-A800YZ are 100% official, original, and obtained directly from Samsung servers.
To flash SM-A800YZ, 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-A800YZ.