
Samsung Galaxy Ace4
The latest firmware for Samsung Galaxy Ace4 (SM-G313MU) is G313MUUBU0AOL2 with Android 4.4.2 (KitKat), released on December 22, 2015 for 17 regions (CSC). Every official firmware build for SM-G313MU, 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/G313MUUBU0AOL2
All 16 builds in our database run Android 4.4.2 (KitKat). The newest build, G313MUUBU0AOL2, was released on December 22, 2015. No new build has appeared for 132 months, so regular updates for this model have most likely ended.
Specifications of SM-G313M, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-G313MY

SM-G316MY

SM-G318MZ

SM-G310HN

SM-G5109
The newest firmware for SM-G313MU runs Android 4.4.2 (KitKat): build G313MUUBU0AOL2, released on December 22, 2015.
The latest build for SM-G313MU, G313MUUBU0AOL2, was released on December 22, 2015 (10 years ago).
SM-G313MU has had no new firmware for 132 months, so regular updates have most likely ended.
Yes, all firmware files for SM-G313MU are 100% official, original, and obtained directly from Samsung servers.
To flash SM-G313MU, 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-G313MU.