Few Sicilian Questions

Does white need to play E4 to use the Sicilian effectively (right now I'm referring to the Dragon variation however I don't think it matters)? I have a match this Tuesday and I'm playing black, I have no idea if just studying the Sicilian will suffice (in the past the guy that I am playing has played many different openings). What (either in your opinion or statistically) is the best opening to learn as black to counter unstructured play? I don't think he studies chess at all and I want to take advantage of the situation. Keep in mind I'm not referring to the amount of traps within the opening, just in general (I guess a mix of tactical and positional play). My last question is; if you are going to play a variation of the Sicilian and your opponent deviates from the main line (I don't mean he starts something advanced, it could be a dumb or uncommon move), is it smart to stick to the main line of the Sicilian you are using or should I just respond in accordance to him?

You always have to respond to your opponent. Don't get too caught up on lines and such, just play good, sound chess in the opening (middle and end game) and you'll be fine.

You must always play in accordance with what your opponent does. That's chess.

considering the sicilian defense is classfied as 1. e4 c5 im pretty sure white needs to play e4 for it to be used effectively.

Is there any type of opening I can learn that would work for a variety of moves white makes?

I was just looking that up, is that the King's Indian Defense? I'm looking at a few You Tube clips and it looks like it works pretty well.

playing sicilian is very difficult or hard defense u must know how to vary ur defense to not be caught in the openning by ur opponent