Extract to your game save directory for RetroArch/Retropie. It should work with both the PCSX-ReARMed and the beetle cores!
This game requires a manual load from the memory card menu for the save to take effect. There's no auto-load from the start like other fighting games.
This game requires a manual load from the memory card menu for the save to take effect. There's no auto-load from the start like other fighting games.
no. 
just having fun.
Whether it can be used with an actual PS2 is something you'd have to do some research on. If anything, what you'd be looking for is probably some guide to convert PCSX2 memory cards/save files to work on a PS2, and that would probably involve using a PS2 with Free McBoot and other tools, I imagine. I can't comment much about the PS2 homebrew scene as I don't have an actual PS2 that I can test that out with. Maybe one of these days...