
Samsung Galaxy A5
The latest firmware for Samsung Galaxy A5 (SM-A500K) is A500KKTU1CQB1 with Android 5.0.2 (Lollipop), released on February 21, 2017 for 1 region (CSC). Every official firmware build for SM-A500K, 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/A500KKTU1CQB1
SM-A500K started on Android 4 and has received 1 major Android upgrade; it now runs Android 5.0.2 (Lollipop). The newest build, A500KKTU1CQB1, was released on February 21, 2017. No new build has appeared for 117 months, so regular updates for this model have most likely ended.
Specifications of SM-A500F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-A185G

SM-A185F

SM-A077F

SM-A085F

SM-A085M

SM-A276B

SM-A576U

SM-A566U
The newest firmware for SM-A500K runs Android 5.0.2 (Lollipop): build A500KKTU1CQB1, released on February 21, 2017.
The latest build for SM-A500K, A500KKTU1CQB1, was released on February 21, 2017 (9 years ago).
SM-A500K has had no new firmware for 117 months, so regular updates have most likely ended.
Yes, all firmware files for SM-A500K are 100% official, original, and obtained directly from Samsung servers.
To flash SM-A500K, 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-A500K.