Abstract—3GPP employs a parallel “Release” approach that provides developers with a stable base for implementing features at a specific moment and then allows for the addition of new capabilities in successive Releases. 3GPP began work on LTE radio-access technology in November 2004, and the initial LTE standards were finalized in December 2007 as part of 3GPP Release 8. With each consecutive iteration, LTE radio-access technology has progressed in many areas, resulting in improved performance and expanded capabilities. Direct device-todevice (D2D) communication was introduced in Release 12 and was later expanded with device-based relaying functionality in Release 13. V2X (Vehicular-to-Vehicular, Vehicular-to-Infrastructure, Vehicular-to-Network) communication is regarded as a critical new use case for cellular networks. 3GPP Release 14 was the first to deliver LTE upgrades in this area, such as improved QoS and V2V support based on the direct device-to-device functionality introduced in Release 12. The paper's main work is to extend examination of the important components of 5G V2X and V12: throughput and Block Error Rate (BLER). We also go over the use cases, system design, evaluation methodology, and simulation propositions for V12 and 5G V2X. Lastly, we compare V2X and V12 advancements, as well as those in Release 12 and Release 14.