None reqire codes - but DARKRAI and SHAYMIN are obtainable in this way -
DARKRAI & SHAYMIN - get the walk anywhere cheat.
DARKRAI - go to CRESSELIA's island. then run accross the water to New...
No. You can use a two tone drum, a source of light, smoke signals - anything that can be understood from a distance and can differentiate between a long signal and a short signal