Registeel doesn't exist in crystal version.
in any version you need a masterball
yes.
In Pokemon Crystal version, you catch it at the Lake of Rage.
Regice: Island Cave (route 105) Regirock: Desert Ruins Registeel: Ancient Tomb (route 120)
You can't. Regice is a Generation III Pokémon, unobtainable in Red, Blue, Yellow, Gold, Silver, and Crystal without serious hacking...which is not recommended. The same goes for its two counterparts, Regirock and Registeel.
you can't but only the gameshark will do!
You could get a shiny Pokemon for crystal but you need luck to catch one ("_")
Trade registeel from ruby,sapphire or emerald to firered.
get lv.100 regigigas through wi-fi event and carry it with you to iron island (registeel) mt. Coronet (regice) and the cave on route 228 (regirock)
no you can not
From the sprout tower at night.
no