You think you know each other very well?
Yes; we've been best friends for over three years. We can read each other very well and can predict how the other will respond to given situations fairly accurately, and I think some of this is just because we do know each other so well.
Do you know each other secrets?
Neither of us have any deep, dark secrets. We know things about each other no one else knows, but I don't think we've kept any "secrets" from each other. If there are things we haven't told each other, it's probably because they're insignificant.
If we asked each other anything, we would tell the truth
Have you guys talked about each others past life?
Yes, especially our childhoods because we didn't meet until high school

That's always fun to talk about, and I feel like I did know him as a little kid. The way we each grew up has played a very crucial role in who we are today, so we've definitely discussed things like how our parents disciplined us, what ages we feel are appropriate for certain rules, etc.
Have there been moments when your significant other told you something that came as a surprise?
Yes. But nothing we've revealed has changed our opinions of or respect/love for the other, nothing shocking that ruined our views of the other person. This is why I know I can trust him; he has had to deal with some pretty deep issues I've had, and he loves and supports me just the same and always has.