The safest and most legal way to enjoy an updated ROM is to use tools like NoNpDrm or Vitamin directly on your own PS Vita to extract your physical cartridge data to your computer.
For enthusiasts running the game on modified hardware, the "updated" experience is significantly improved through community mods: mortal kombat 9 ps vita rom updated
If MK9 refuses to boot past a black screen on your emulator, ensure you have installed both the modules/firmware font packages within Vita3K. Additionally, switching the graphics backend from OpenGL to Vulkan fixes the vast majority of rendering crashes. The safest and most legal way to enjoy