I'll answer as best I can from memory.
1:is the universe infinite?
... Yes and no, in theory, if you travel in a straight line across the universe you would eventually end up where you began.
Think of it as a Sphere, with you travelling on the inside.
2:What would happen if you were to go into a black hole?
Bad, Bad things.
Stretched to an infinite point, and torn apart by the gravity.
3: Is it possible there is life, other than on our planet, in the universe?
Yes, Life is pre-emminent on earth, so one can assume it is elswhere, weve just not found any.
4: How did the universe start?
The big bang (Or multiple big bangs depending on whom you ask)
All matter and energy and whatnot in the universe was condensed into a single point of existance, something occured which caused said ickle ball to explode, creating the universe as we know it (After quite a bit of time mindyou)
The Universe is also some Ten Billion years old.
Note: There is a before the Universe, its just nothing that we can comprehend.
5: What might cause the destruction of our solar system?
Super Nova (Large stars detonating in their death throes)
Not much else would actually destroy a solar system.
6: What might cause the destruction of the entire universe?
Not a lot, Anti-matter cascade perhaps (A possible side effect of using Particle accellerators, albeit the odds for it happening are... Uncalculable)
7: Is there such things as parallel universes?
For every possible action and for every possible moment their is an alternate reality.
8: How exactly does gravity work?
Think of it like putting a weight upon some foam, the weight drops down a certain distance and the foam around it follows it as its dragged down.
Gravity works like that, but with a whole load more dimensions.
9:If it is infinite, what is it expanding into ? If it isn't infinite, what's outside of the universe?
Its expanding into nothing. a void.
To blatantly steal from doctor Who;
"no up, no down, no left no right, no light no dark. nothing."
Sorry for the scant answers, my books and sources are elswhere and I'm working from memory.