1: No one knows. People who claim they know are 100% full of shit. Religious people think there is a god because that's whats been told to them by their parents, people around them, church, bible (or that religion's book of choice). People who don't believe in god are looking at facts, science, logic and making the best guess they can.
1a. Yes, I believe it that's the only way to prove there's a god, besides him making a personal appearance.
2: I don't know, and no one really does. I personally believe that there has always been matter. It's a really hard thing for humans to comprehend...always was and always will be. We like to think of things having a beginning and an end.
2a: It's hard for me to think that there is a sound basis for intelligent design. Early humans were looking for answers, and with the intelligence, tools and science available to them, that's the best they could come up with. It's not impossible though.
3: This is probably my main argument as to why I think religion is bullshit. You have god that knows how everything is going to end up, he knows how you think, what your future actions will be...but then he tells you that your decisions and actions will determine whether you go to heaven or hell. "I'm going to create Jim, he will be a murderer, he will kill an innocent 2 year old that doesn't even have the mental ability to know the difference between right and wrong. So the 2 year old gets the ultimate punishment for no reason and Jim has no choice to be a murderer because that's how he was pre-programmed. PS Everyone has free will"