there is no green type pokemon. Sorry
Ground type Pokemon can beat Electric type Pokemon easily.
You can beat it with Ground type Pokemon or Fire type Pokemon easily.
In the 3rd generation of Pokemon (Sapphire, Ruby, Emerald, Leaf Green, and Fire Red) it is easily agreed upon Pokemon users that a fire type of Pokemon is the best for advancing through the game easily. However, it is best to have a wide range of Pokemon types in your party because every Pokemon type has type advantages and disadvantages. So if your person your battling has a Pokemon that has a type advantage over you, (example: he has a water Pokemon and you have a fire Pokemon) switch out to a better one. This is very important for the elite four since each person has a different type of Pokemon.
This Pokemon cannot evolve. You can easily search for info on Bulbapedia.
Ice type Pokemon can easily defeat lance's Pokemon also for his gyrados and aerodactyl you can use an electric type.
Ditto is a genderless Normal type Pokemon from the first generation. In Pokemon Leaf Green, it can be found in the wild on Routes 13, 14, and 15, at the Pokemon Mansion, or in Cerulean Cave.
Steel type does not exist in leaf green.
You find it in pokemon! it's obvious!
Any unevolved bug type pokemon.
Poison type pokemon, other trainers in the gym also have psychic but again the leader has poison type
anywhere
On the show Pokemon an electric type/ground type like Pikacu is stronger than a flying type.