they say 3DS to show they WORK on a 3DS, as the 3DS blocks flashcards
the only 3DS Games Flashcards are Gateway3DS, MT-Card, R4i Gold 3DS Deluxe, 3DSLink, Orange3DS (listed in order of best compatibility)
and yes as above says
your 3DS must be on 4.1>4.5 Firmware
and no you cannot downgrade...