for future reference in regards to frauds and bootlegs:
1, look online for a known retail list of cartridges, it makes sense the 'devs' (nintendo in this case) keep a list of releases, and regional variations. one of the lists are public, the other is pcb revisions. (game label should have the disk id on it and correlate that with online searches.)
2, the pcb itself. i have a few bootlegs, and the easiest telltale sign, is NO signs of the hardware producer (nintendo again) and copyrighted chips.
3, the quality of build can be shit vs official, but not always.
...
years ago, was given a megadrive cartridge that was a bootleg, had three games. (1, altered beast. 2, golden axe. 3, streets of rage.)
there was a red button on the top of the cartridge, used for a menu reset to select the other games.
normal console resets only loaded the last game selected. (the sega splash was obscured, perhaps a flimsy attempt to dodge legal teams?!)
i can't think of any retail cartridge having such a feature, or behaving that way.
...
i don't have it anymore, but i do have two (maybe three) pirated gb? cartridges, they're stuffed away somewhere, and i need to dig em out.
i do know one of em is a translucent blue pokemon pos for gbc, and a 101-in-1 ripoff for the dmg. (same as with the megadrive rip, obscured nintendo logo, cept the 101-in-1 cartridge had many duplicate games as parent/alternate roms.)

[edit]
typo.