You're going to have to trade over from the different versions, but you cannot have Black and White Pokemon in the other games.
In the first game, you have to catch all legendaries and battle every trainer you encounter
pearl
No. None of the legendaries, including latios and latias, can breed in any game third generation or beyond.
No, you can't find all the legendaries in Diamond. There isn't a Pokemon game with all the legendaries in it. You can capture 8 legendaries in Diamond, f you want all the legendaries, you'll need to visit events, trade or migrate them.
Depending on rare, there are actual rare Pokemon and Legendaries. There is a rare Pokemon about in every location and what I mean is by the low encounter rate. Legendaries can be found by certain interactions in different places. I suggest using Bulbapedia, Serebii, or Azurilland to find these Pokemon depending on the game you are playing, for some "rare" Pokemon can be common in other games.
go to this page http://www.serebii.net/diamondpearl/legendaries.shtml this page has all the legendaries you can normally catch in in Pokemon diamond/pearl all other legendaries you have to transfer from a 3rd generation game
More legendaries like Pokemon Heartgold and Soulsilver.
Pokemon ruby, sapphire, and emerald. The legendaries are groudon kyogre and rayquaza.
You die
In every mainstream Pokemon game since Gold and Silver, there has been a Pokemon daycare in the middle of the game's storyline; if you leave two similar Pokemon of a different gender or a Pokemon and a ditto in the daycare, they will lay an egg. Legendaries and genderless Pokemon cannot lay eggs. In Pokemon Diamond and Pearl, you can track egg laying with the Daycare app.
All you need to do to get shiny legendaries is save your game right before you fight a legendary and if it isn't shiny than just keep shutting your game off and turning it back on. This works for all versions starting with Pokemon Silver and Pokemon Gold
The strongest Pokemon is probably one of these three. Rayquaza Groudon or Kyoger. These three are the main legendaries of this game.