yes. regirock, ice, and steel are classified as legendaries.
the regis rayquaza latias latios and kyoger
If you flee from one of the Regis in Pokemon Ruby it will disappear from the game. This is the same for all Legendary Pokemon in all Pokemon games. The Roaming Legendary Pokemon are an exception as they can flee from battle without disappearing.
no legendary Pokemon or genderless Pokemon can make eggs/breed. hope i help :)
all i know is how to get the regis and latios or latias.
ruby=groudon+raquaza+latios+the regis sapphire=kyogre+raquaza+latias+the regis emerald=raquaza+groudon+kyogre+latios or latias+the regis
u need 2 go beat the towers of wat legendary Pokemon u want 2 have and 2 get any of the regis u need 2 do the regi quest
RayquazaRare or Legendary? Legendary, the same in Ruby and Sapphire. Groudon, Kyogre, Rayquaza, Latios/Latias, the Regis. Not very many, rare pokemon,besides what you can get after the national dex, like sudowoodo, or smeargle.
dialga palkia uxie azelf mesprit regis regigigas deoxys celeby manaphy phionie etc.
This depends on which Pokemon you speak of. If you killed Groudon, one of the regis or Rayquasa, then you can't get them. If it was Latios or Latias that "fled" from a battle you can be sure you will run into them again sometime in the future.
some Pokemon u can get by just findig the for example regis, groudon, rayqaza, kyogre and latios/latias. if u wanna catch mew, deoxys you have to have a special event.
Milotic, Pikachu (with Light Ball), Salamence, Altaria, Kingdra, the three Regis (They aren't legendaries) etc...
You cant other than the regis. you have to use an action replay. if you want the code for it, then look it up at supercheats.com