Hi can anyone please suggest a good NDS Slot 2 flashcart that has good compatibility with most gba roms and can work with most Slot 1s? I heard that some Slot 2 carts can only work with their Slot 1 'older brothers'. Is this true?
That depends. I only have experience with an R4. If you own a DSLite, you can get the EZFlash 3-in-1 for your R4 (and it'll prolly work with the M3DSS too, but I don't know...) It only works in a DSLite though, so if you have a DSPhat you're outta luck.