You can't get to the johto region in firered.
You can NEVER go to the Hoenn region in LeafGreen or FireRed. You may trade with Ruby/Sapphire/Emerald, but NO!!!
Taillow is a 3rd Generation Pokemon or a Hoenn region exclusive Pokemon meaning that Firered version which takes place in the Kanto region cannot capture it. All 3rd Generation Pokemon must be traded to Firered from either Ruby, Sapphire or Emerald.
Click new game and there you go.
corphish is a Pokemon that is native to the hoenn region
in firered and leafgreen you play in the kanto region
You can't get to the johto region in firered.
kanto
Whirl islands are in the johto region which is not in firered.
You can NEVER go to the Hoenn region in LeafGreen or FireRed. You may trade with Ruby/Sapphire/Emerald, but NO!!!
you cannot
Kanto
You're in the Kanto region in LeafGreen and FireRed.
Oldale town is in the hoenn region which you can't go to in firered.
You can't
you cant, sorry.
It's Kanto. ;)