Is it possible to play games like Legend of Zelda: Four Swords Adventure with friends on the Nintendo DS system? Are you able to use the wireless feature to play together with multiple Nintendo DS systems or do you have to use a link cable like on the GameBoy Advance?
No, it is not possible to be able to link Game Boy Advance games on the Nintendo DS. Unless the games you want to play have the multiplayer feature that only uses one unit, you can only play them as one player on the DS, as the GBA games are not able to use the DS wireless features and the DS does not have a connector for a link cable.
I believe that you can purchase a wireless adapter for the GBA and see if it would connect with the wireless feature in your DS. I have not tried this yet but I think it might be possible.