Porting GTA Vice City to the PS Vita is no easy feat. The game's original code was written for the PlayStation 2, which has a vastly different architecture than the PS Vita. The developers have had to use a combination of reverse engineering and porting techniques to get the game running on the PS Vita.
Unlike the original mobile or console versions, the Vita port offers several modern "quality of life" improvements: gta vice city ps vita github