After beating Erika in Celadon City, you can do many things. By getting Hot Tea from an old lady in a building in Celadon, you can access Saffron city through the gate. Also, you can talk to the Rocket Grunt in the Game Corner and go into the Rocket's Hideout and defeat Giovanni to get the Silph Scope. Then, if you have not already, you can climb the Pokemon Tower in Lavender Town and defeat Team Rocket to "rescue" Mr. Fuji and get the Poke Flute. The last thing you can do is head south from either Celadon or Lavender to Fuchsia and challenge Koga for the fifth badge. Please keep in mind that ALL of this is required at one point or another.
Chat with our AI personalities
The fourth gym at Pokemon fire red is grass type gym
Cinnabar Island
yes
probably
it is on the B1 floor, on the table.