
Samsung Galaxy A3(2016)
The latest firmware for Samsung Galaxy A3(2016) (SM-A310N0) is A310N0KOS1CTJ2 with Android 7.0 (Nougat), released on November 8, 2020 for 1 region (CSC). Every official firmware build for SM-A310N0, 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/A310N0KOS1CTJ2
SM-A310N0 started on Android 5 and has received 2 major Android upgrades; it now runs Android 7.0 (Nougat). The newest build, A310N0KOS1CTJ2, was released on November 8, 2020. No new build has appeared for 72 months, so regular updates for this model have most likely ended.
Specifications of SM-A310, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-A310X

SM-A315N

SM-A320X

SM-A300XU

SM-A326K
The newest firmware for SM-A310N0 runs Android 7.0 (Nougat): build A310N0KOS1CTJ2, released on November 8, 2020.
The latest build for SM-A310N0, A310N0KOS1CTJ2, was released on November 8, 2020 (5 years ago).
SM-A310N0 has had no new firmware for 72 months, so regular updates have most likely ended.
Yes, all firmware files for SM-A310N0 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-A310N0, 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-A310N0.