In Pokemon firered you can't, but in Pokemon leafgreen you can get it then trade it to Pokemon firered.
To get Pokemon firered on PC download a vba and Pokemon firered ROM
Yes there are shiny Pokemon in firered
It is not possible to get a ninth badge in Pokemon FireRed. You can only get eight badges in Pokemon FireRed.
You cannot get it in Pokemon FireRed. It doesn't matter because it is not necessary in Pokemon FireRed.
gsc stands for gold silver and crystyl because they are all Pokemon games so gsc Pokemon are all Pokemon from Pokemon gold Pokemon silver and Pokemon crystyl and there it is you know the answer forever.
You can get Gold, Silver and Crystal Pokemon by trading them with either FireRed or LeafGreen, then trade those Pokemon in FireRed and LeafGreen with your Emerald. Or after you've defeated the League go to the Safari Zone and the area that was blocked off, can now be explored, it has Johto Pokemon to a certain extent.
Gold / Silver / Crystal
You can get Pokemon from the Honnen and Kanto region, and after beating the Elite Four you can get certain GSC Pokemon.
In Pokemon firered you can't, but in Pokemon leafgreen you can get it then trade it to Pokemon firered.
Same reason you fight Red in GSC.
There is no Pokemon convention in firered.
To get Pokemon firered on PC download a vba and Pokemon firered ROM
Yes there are shiny Pokemon in firered
It is not possible to get a ninth badge in Pokemon FireRed. You can only get eight badges in Pokemon FireRed.
You cannot get it in Pokemon FireRed. It doesn't matter because it is not necessary in Pokemon FireRed.
Celebi cannot be found in Pokemon FireRed. The only way to get Celebi in Pokemon FireRed is receiving it from an event distribution. These events are sadly no longer supported for Pokemon FireRed.