you need to get the badge in fuschia city
the badge you need is the 4th one and also if you have not already you can get surf in the dance theater.
The 7th badge.
Hearthome gym
In Pokémon FireRed, for defeating Brock, his Badge will allow you the use of the Flash HM, Misty's Badge will allow you to use the Cut HM, Lt. Surge's Badge will allow you the use of the Fly HM, Erika's Badge will allow you the use of the Strength HM and Koga's Badge will allow you the use of the Surf HM.
You win surf for finding the hidden house in the safari zone. To use surf, you need the Soul Badge from Koga of Fuchsia City.
On cinnabar island. You can get to Cinnabar by using surf from Pallet Town. To use surf, you need to get Fuschias gym badge.
you need to get the badge in fuschia city
the badge you need is the 4th one and also if you have not already you can get surf in the dance theater.
The 7th badge.
6th gym badge
Hearthome gym
In Pokémon FireRed, for defeating Brock, his Badge will allow you the use of the Flash HM, Misty's Badge will allow you to use the Cut HM, Lt. Surge's Badge will allow you the use of the Fly HM, Erika's Badge will allow you the use of the Strength HM and Koga's Badge will allow you the use of the Surf HM.
3
You can use the move strength in Pokémon to move boulders. You can use strength in FireRed after getting the rainbow badge.
You need the soul badge that is obtained from defeating the Fuschia city gym leader Koga in order to use surf outside of battle.
You need at least the first badge to use flash.