you cannot
You can NEVER go to the Hoenn region in LeafGreen or FireRed. You may trade with Ruby/Sapphire/Emerald, but NO!!!
corphish is a Pokemon that is native to the hoenn region
There are no space centers in Firered the only space centers that exist in the Pokemon world are located in the Hoenn region at Mossdeep City.
The island of Hoenn is not available in Pokemon LeafGreen, unfortunately. FireRed and LeafGreen are limited to the region of Kanto, while Ruby, Sapphire, and Emerald are currently the only Pokemon games that take place in Hoenn.
you can't catch any hoenn Pokemon in firered or leafgreen you must trade hoenn Pokemon from ruby or sapphire or emerald to leafgreen or firered.
Its impossible to capture any hoenn Pokemon in firered so you have to trade hoenn Pokemon from ruby, sapphire and emerald to get them.
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.
None
Its impossible to catch any hoenn Pokemon in firered if you want hoenn Pokemon like groudon and kyogre trade them from ruby, sapphire or emerald to receive them in firered.
All the Pokemon that didn't exist in that particular region. Example in firered and leafgreen you can get johto and hoenn Pokemon like lugia or rayquaza. In diamond and pearl you can get stuff from kanto and johto and hoenn.
All Hoenn Pokemon (bagon is just one of them) cannot be obtained in either Firered or Leafgreen you will need one of the versions that resides within the Hoenn region those versions are: Ruby, Sapphire and Emerald.
The Hoenn Region is available in the pokemon versions Ruby, Sapphire, and Emerald.