A: No. The original GBA cartridge only supported 2 players via the link cable. Emulators cannot add more players than the code allows.
If you want to own the original cartridge for your collection, it is available from various retro retailers: Need for Speed: Underground GBA Play Need For Speed Underground GBA Online
The GBA version is not better than the PS2 version, but it is different . It is faster, tighter, and arguably more pure as an arcade experience. By leveraging RetroArch and NetPlay, you are not just playing a game; you are preserving a unique multiplayer heritage that would otherwise be lost to dead link cables. Play Need For Speed Underground GBA Online