ok i want to know if i transfer my roms to the flash cart, can i be able to link to other gba.
for example if i want to link together with someone else to play FFT

I never tried it myself but Im pretty sure you could do that. I don't think the gba has any protection mechanisms against that sort of thing.

Yes, the gba cant tell the difference between a flashcart and a real game so i couldnt see you being unable to link unless of cause the game you have on the flash cart is corrupt somehow