Brock the rock gym leader
Pewter City
you can't get mamoswine in Pokemon leaf green because it doesn't exist in leaf green
After beating Giovanni the last time as the gym leader you should get the TM earthquake.
behind the door is leaf green u enter the Pokemon leaf green world
no
Brock the rock gym leader
Pewter City
i think it iz erica she uses leaf Pokemon so either use ice or fire Pokemon
Poison type pokemon, other trainers in the gym also have psychic but again the leader has poison type
to find a legendary Pokemon
in the city that you find the grass gym leader
Its in virdian city. The gym leader is Govanni, and he uses ground and fighting pokemon.
Giovanni is the leader of team rocket and the 8th gym leader in fire red and leaf green.
he is in the gym in vermillion city on fire red and/or leaf green
beat the gym leader
You can get Pollywhirl in Pokemon Leaf Green in Virdian City.