There is no legendary Pokemon in Challenger's Cave, only one person who said one used to live there.
In Pokemon black you catch RESHIRAM and TORNADUS In Pokemon white you catch ZEKROM and THUNDERUS Sources : myself
2
Pokemon Black: Last gym leader is male You catch the white legedary Different wild Pokemon Pokemon White: Last gym leader is a female You catch a black legendary Different wild pokemon May be more, but these are just the most obvious ones. Only very minor things, though!
you first have to catch/defeat the legendary pokemon cobalion in mistralion cave you catch virizion in pinwheel forest
You can only catch the rest of the Legendary Musketeer Trio after you first catch Cobalion in Mistralton Cave located on Route 6.
You have to defeat the elite four then you can catch the legendary
to catch zapdos in pokemon black you have to have every legendary pokemon
you can catch as many legendary Pokemon but only once unless you have it on the computer
You catch them with a ultra ball
Zekrom in Pokemon White and Resharim in Pokemon Black.
In Pokemon black you catch RESHIRAM and TORNADUS In Pokemon white you catch ZEKROM and THUNDERUS Sources : myself
None
In black you can catch Reshiram and tornados. In white you can catch Zekrom and thunderos.
Yes, Reshiram is Black's legendary. You will not be able to catch Zekrom though.
Well it depends what legendary you mean. There are a lot and it would be hard to tell where they all are.
Yes, you catch it in the Giant Chasm.
I put a link to guide on all the legendary pokemon in Pokemon Black in the related links.