I think you can get one at the Safari Zone. Go to the first patch of grass you see. I have caught them there before.
Breed a female pikachu with any Pokemon from its breeding group or any pickachu with a ditto.
trophy garden
Pokemon ruby's version IS Pokemon ruby.
The Pickachu in Pokemone Platinum is in the Trophy Garden.
no you cant,the only way you can get pickachu is by transfering in from pokemon diamond,pearl or platinum
The Viridian Forest and I think Route 2
yes, like pickachu, eevee, and clafairy.
pickachu
In Pokemon Soulsilver you catch pickachu in the Viridian Forest during the day.
Simply put 2 pikachu in the daycare which is located west of mauville city also east of verandturf town.
somewhere
Arceus is not possible to find in Pokemon Ruby. It was released in 2007 with Pokemon Diamond and Pearl