Here's three (for US):
Enter your code on Nintendo eShop:
B0HBGJW544VC7DHV
It’s dangerous to go alone!
Bring two friends along by giving them these free demo codes.
B0HBJ3V81PVDHJBP
B0HX4M2G29SCQ0X5
I don't think there is something like that. You can (possibly) try private servers of that game you're talking about. There are no ROMs or such for MMORPGs. Your best bet would be cheating on the game.
1.) Pokemon Black 2/White 2
2.) OkamiDEN
3.) Kirby Squeak Squad
4.) The World Ends With You
5.) Megaman Zero Collection (Yeah. Ports. But rushing through all four is fun.)/ Megaman ZX Advent