Get the key from the basement of the mansion next to the gym.
After obtaining the other 7 badges you return to Viridian City and the gym will be open.
You must beat the seven gym leaders, the elite four, and your rival. Then you have to capture 60 Pokemon to get your Rainbow pass the will allow you to travel to Island 7 in Pokemon FireRed.
no
go to cinnabar island then go into Pokemon mansion go through here to get the secret key which opens the 7th gym.
it is in saffron
In his Gym in Cinnabar.
the thunder gym in in vermillion city
You have to beat the 2nd gym.
In the cinnibar island gym.
beat the gym leader
there is no gym leader in lavender town
The fourth gym at Pokemon fire red is grass type gym