so i tried this on libretro-fba-next and it worked for me. here’s what i did:
– load street fighter III third strike
– go into retroarch menu (select + x on my snes controller)
– quick menu > core options
– changed the service mode access to ‘hold start’
– exited the menu
– held start to enter service menu
– went to system options and put free play mode on
– chose ‘save and exit’ in the service
– game started and freeplay was on
– exited game (start + select) and reloaded.. freeplay is still on

it saves the eeprom state in the /roms/fba/ directory – GAMENAME.fs

i didn’t try with a CPS2 game – shouldn’t make a difference (i think??)

i’ll add this all to the wiki in a bit