Do Nintendo 3DS Games Work on DS / DS Lite / DSi? No

No. 3DS games are physically and electronically incompatible with any DS-family console (DS, DS Lite, DSi, DSi XL).

• Different cartridge shape: 3DS cards have a tab preventing insertion into DS slots.
• Different architecture: 3DS uses ARM11/ARM9 CPUs, GPU, and firmware absent on DS.
• 3D display: Games rely on the autostereoscopic screen.

Reverse works: All DS games play on 3DS / 3DS XL / 2DS (backward compatible).