I can't answer all of the above questions just yet, but I do have a bit of an explaination of the question "How did you become you?"
I'm a heavy believer that it's our experiences that mold us into the people we are today. From the minute we're born it's the circumstances and events
that we encounter that transform us be it through idols, upbringing, friends etc. The old saying "no two people are the same" applies to this, in that
it's impossible to recreate exactly the same events for another person (infinite number of possibilities), not to mention the fact that they may react differently
in different scenarios. Though genetics lay the ground work, I think it's the things around us in our daily life and how we interpret us that makes us who we are.

*how we interpret them*, sorry :(

my answer for this question is pretty simple. i think that every decision i make everyday, is what causes me to be me, because the decisions i make probably wont be made by another, so they are unique to.

i became me from all the things around me, from decisons people have made to, my own givin choices, my friends and family have helped alot to, sure still we are all differnt, but everything in our everyday life, can make us who we are. and help us out in a great matter, you just need to take it easy and step slowly in life. and you will learn lots. and it all in the end. makes you who you are today.

I agree with Devin when he said that who we are is sort of like our ground work; I mean this is the whole nature vs. nurture. I think that nature plays a small role in who we are- it's like the video about the two twins that grew up to be a lot alike despite their different environment. But in reality, what are the chances of that? I think that we are initially who we REALLY are when we are born, and over time, we tend to loose that sense of who we are because of our experiences.
No doubt your experience/nurture influences who you are- for example, if you start singing when your five and by the time your twelve, you find out you have cancer and can no longer sing, who you are will be very different than who you could have become- maybe you'll be bitter instead of becoming famous and having a big ego.