The are more than three legendary Pokemon infact there are 34:
The First Generation:
Zapdos, Articuno and Moltres (Legendary Birds)
Mew and Mewtwo
The second Gereration:
Raikou, Entei and Suicune (Legendary Beasts)
Lugia and Ho-Oh
Celibi
The Thrid Generation:
Regirock, Regice and Registeel (Legendary Golems)
Latias and Latios
Kyogre, Groudon and Rayquaza (Weather Trio)
Jirachi
Deoxys
The Fourth Generation:
Uxie, Mesprit and Azelf (Three Lake Guardians)
Diagla, Palkia and Giratina
Heatran
Regigigas
Cresselia
Phione and Manaphy
Darkrai
Shaymin
Arceus
The Fifth Generation:
Victini
Cobalion, Terrakion and Verizion (Three Musketeers)
Tornadus, Thundurus and Landurus (Kami Trio)
Reshiram and Zekrom
Kyurem
Keldeo
Meloetta
Genesect
they are kyogre, reyquaza, and latias.
To get the three beings and Dialga, you must beat Dialga and then battle them again.
After the big battle with all the three legendaries, you cant, unless you have a cheat.
Rayquaza, Kyrogre, Groudon, Latias or Latios, all three regis, and deoxys/jirachi if you can get them :P
use hacks:P:P:P
These are the legendaries in diamond that you can get without any cheats:DialgaUxieMespriteAzelfHeatranRegigigasGiratinaCresseliaRotom
If you are talking about the one to get up Mt. Coronet you have to free the three legendaries
Moltres, zapados, and articuno are the three main legendaries in leaf green/fire red
the legendaries are dialga, palkia, heatran (sad but true), cresselia, giratina, darkrai, shaymin, manaphy, phione, shaymin and arceus oh and the three legendaries too, uxie mesprit and azelf oh and regigigas
All legendaries can be shiny when soft resetting.
Unfortunately not; Legendaries can't breed at all, not even with Ditto.
There aren't any samurai legedaries in B/W, but there are three legendaries based off the Three Muskateirs; Virizion, Cobalion, and Terakion.