Samsung Galaxy Ace 4 LTE (SM-G313HY) Firmware Overview
The archive lists 3 official builds for the Samsung Galaxy Ace 4 LTE across 1 region (CSC). The newest one is G313HYXXU0ANK1, released November 21, 2014 with Android 4.4.2. It is a feature update on bootloader binary 0: once a phone runs it, firmware with a lower binary can no longer be flashed (how to read a build number).
How to Flash SM-G313HY Firmware
Put the Samsung Galaxy Ace 4 LTE into Download Mode, load the BL, AP, CP and CSC files into Odin on a Windows PC and press Start. Pick a build with the same or a higher Bit than the one installed — a lower bootloader binary will be rejected.