You can get Rayquaza on Soulsilver if you get both Kyogre and Groudon. Then you get the jade orb from some guy and go to the same cave that you got Groudon. To get Kyogre you have to get it by trading.
no you can not if else you had like 10 dialga or something it is just not possible
you can unless u get a special event from gamestop or something
Latios
Sorry you can't catch mew, once you advance in the game you can catch a legendary/special mewtwo (evolved mew).
Well, I guess you mean "Soul Silver", and the main legendary Pokemon is Lugia, Water/Flying-Type.
the only legendary that you can breed is manaphy. and that will result in a phione.
over 9000
you can not get regirock in soul silver but in platinum you can in a special event.
to get the legendary (lugia) you must go to the whirlpool islands and on one of the islands you will find lugia
Probably either Mewtwo or Rayquaza.
ranges from 40(legendary dogs) to 70(ho-oh for you, mewtwo, ect.)
you have to look in places where a legendary might live (example: Zapdos=power plant)