Realfun 3

MegaFlashRomSccPlus is the required rom type / mapper for the rom itself, no need to add an extra MegaFlashRomScc+, that will not work anyway as there is no SCC detection.
(also you may need to delete an old .SRAM image "openMSX\persistent\roms\rf3rep.rom\" before the new one takes)

There is no auto detection for complex mapper types. These would be covered by the ROM database.