Very very little.
You have a 1/8000 chances to see any shiny Pokemon find an area where you can find Aron alot and wait until its shiny then catch it.
nothing
See related link(s) for the website to download Pokemon Sapphire.
I think you need to see them all.
Watch the TV.
Route 228
see/catch every Pokemon
Its easy just go to serebii.net and you will see a list of Pokemon games click on ruby/Sapphire and then once you get to that page press new Pokemon or ruby/Sapphire pokedex then youll see a list of Pokemon.
dig down where you see a pickachu
Shiny Pokemon are rare Pokemon that you can rarely find. When you see one it'll have different colors and a circle of stars will show.
At the first pile of grass you see
You cannot see Kyogre in Pokemon Ruby because it's a version exclusive to Sapphire and can be found in Emerald also.