Getting started in VG

[PokemonPizzaParty]

Hey people, so, I want to get started in vgc, but I have a few questions, and I have no idea where to start.

Question 1: Can you use pokemon in competitions that are from BW only?
Question 2: Can you use legendary pokemon?
Question 3: How many pokemon do you need?
Question 4: What type of battles are they? (double, triple etc.)
and finally Question 5: What level should/at least your pokemon be?

I have the Pokemon white and soul silver, and have finished each game, but I have no idea what you need to make a decent team. When I tried playing before, I lost miserably, having no idea what I was doing. So I just want to know where to start. I don't have every Pokemon, but I do have a nice selection, so if you can just help me with what are some good Pokemon I should start using, I'll go find them.
Thanks in advance!
-PokemonPizzaparty okeball:

 

[ultimatedra]

Wow - All this can be found by...you know...reading the rules that Pokemon put out.
I am going to link you to the rules, and let you read them for yourself. Start on page 26. Don't be lazy.
http://assets5.pokemon.com/assets/cms/pdf/op/tournaments/2012/pokemon_tournament_rules_11_1_2011.pdf

ALL 5 of your questions can be found in that document. As for what pokemon to use, utilize the articles that have been put out for you:

Regis_Neo's VGC Guide
Pokemon.com's fall regional strategy's

 

[PokemonPizzaParty]

^ Thanks for the links!