you do it like you did the first time.
You win one when you beat a Master rank Pokemon contest for the second time with the same Pokemon.
all you have to do is beat the Pokemon league 1 time its simple.
Beat then one at the time
Finish your Pokedex And Beat The Elite Four once then the second time they have stronger Pokemon
nothing.
get the ruby sapphire
You can battle your friend at any time you don't have to beat the elite four.
get strong EFFECTIVE Pokemon
NOOOOOOOOOOOOOOO just get your starter Pokemon beat may for the first time and catch a nuther Pokemon you need to own 2 Pokemon in order to trade and you need a link cabel or wire less conecter. Wirless adapters don't work for Pokemon sapphire or Pokemon ruby you have to use a GBA to GBA link cable.
after you beat the Pokemon league chapion may and professor birch will congratulate you. professor birch will also check your pokedex.
Go back and get through the map you first fought them on.
There is no way to buy any masterballs in any Pokemon version. However, you can have a Pokemon from another version trade over a masterball, and in ruby, sapphire, and emerald, you can get a second masterball at the lilycove dept. store lottery.