Yes but the only one you can catch lugia
catch them
you don't need legendaries to catch other legendaries. just get a team of Pokemon around the level of the legendary you are trying to catch. weaken it until it is about to faint, and if you can put it to sleep or paralyze it, do that. then just keep throwing ultra balls until you catch it. just in case you don't catch, i recommend saving right before you start a battle with a legendary.
the best way to GET legendaries is by action replay. and the best way to CATCH legendaries is lowering there hp and catching them. or choosing the right pokeball:masterball,ultaball,repeatball,greatball,and pokeball.
none
nope.
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
arceus
You cannot catch both legendaries with a single game.
If you mean legendaries, then no.
The legendaries you can catch in Pokemon Ruby without trading or going to an event are Groundon, Rayquaza, Latios, Regice, Regirock, and Registeel.
g;r;g;g
Yes, you neeb a secret slab or a mystery part to get legendaries in the final maze