These carts play DS games, they do not play 3DS games.
Each time the console gets an upgrade (DS to DSi; DSxl; 3DS; etc) some of the carts stop working, and manufacturers use it as a marketing opportunity.
Cards usually tack '3ds' on the name. EG: "R4i3DS". But these just play DS games on the 3DS. (Some of them include GBA emulation functionality; nothing could play GBA games on the NDS cart slot until recently.)
These carts play DS games, they do not play 3DS games.
Each time the console gets an upgrade (DS to DSi; DSxl; 3DS; etc) some of the carts stop working, and manufacturers use it as a marketing opportunity.
Cards usually tack '3ds' on the name. EG: "R4i3DS". But these just play DS games on the 3DS. (Some of them include GBA emulation functionality; nothing could play GBA games on the NDS cart slot until recently.)