“V2” is not a real thing. Neither is “V4” as some people call it. The most succinct name that is accurate and avoids confusion is “Cortex system” or “Cortex control system.” If you want to be pedantic, it is the “VEX ARM® Cortex®-based Microcontroller electronics platform and control system,” but even VEX is calling it the “Cortex control system,” shortened down to “Cortex” when context allows:
See here for more information (from an official source even!) on VEX microcontrollers throughout history: