The fourth badge. It's in Lavaridge town. You'll need to use the cable car north-west of Mauville.
You get it from a lady in vendanturf town, and use it in front of big boulders. you need the heat badge to use it out of battle.
You don't need a badge to get strength but you need a badge to use strength and that badge is the rainbowbadge and that is the 4th one in celadon city.
You can use the move strength in Pokémon to move boulders. You can use strength in FireRed after getting the rainbow badge.
The mine badge.
Strength will activate when you get the RainbowBadge.
You get it from a lady in vendanturf town, and use it in front of big boulders. you need the heat badge to use it out of battle.
You don't need a badge to get strength but you need a badge to use strength and that badge is the rainbowbadge and that is the 4th one in celadon city.
You can use the move strength in Pokémon to move boulders. You can use strength in FireRed after getting the rainbow badge.
The mine badge.
Strength will activate when you get the RainbowBadge.
The fourth gym.
In Pokémon Alpha Sapphire, the Strength HM (HM04) is obtained from a character named Wally in Mauville City after you defeat the Gym Leader, Wattson. You need to have the Cascade Badge to use Strength outside of battle. Once you have the HM, you can teach it to a compatible Pokémon and use it to move boulders in certain locations throughout the game.
you need the fire badge in lavenderige town kk good luck
You need the 4th badge first to use it.
The fourth one.
You need the cobble badge.
Use strength. I believe you need the Water gym badge