What wonderful questions! I'm so glad you wrote in. The information you are seeking will be helpful for everyone. First off, about communicating with your guardian. Yes, it is good if you can get to a point where you can converse with him or her whenever you'd like. It is helpful and can only make you feel better about things. Following the information on this site will help you tremendously in that area. As for your other questions...
I know I say this all the time, but I think its something that needs more exposure anyway, so I'll say it again, "ANYTHING IS POSSIBLE!". Angels can choose us, we can choose them, angels can have one soul to take care of or many souls. And yes, angels might have been on this planet as humans. Let me tell you what I have found to be true about my guardian angel and maybe that information will help you.
I really only know a few things about Michael. I know he's been with me my whole life, I just didn't realize what he was until about 8 years ago. I know he's male and I know he loves me as much as God loves me. I've gotten to a point with Michael where I can converse with him whenever I'd like, but I don't do it when it could be hazardous (while I'm driving, etc...). I feel that Michael is not the only angel that helps me through this life, but I feel that he is "the boss" per say. I have experienced many things during my last 8 years of metaphysical motion, but one thing that's always been true is that Michael has always been there to help me.
Now, folks could argue that God or Jesus should be the one there to help you. Well, my answer to that is that Michael is one of God's creations and he serves his purpose just like the sun, the wind, and the water serve theirs. He's here to help me. Of course, Jesus has a place in my life, too. Jesus is my savior, and its because of him that I'm able to do what I do. Without his influence and his place in my life I would be nothing. Aside from all that, Jesus is my security blanket. I know that no matter what I do, no matter what I think, no matter what, I'm able to do whatever I want here, and in the hereafter, because of the sacrifices that he made.
I happen to believe that Michael and I have had experiences together where we existed in the same "world" or "dimension" per say. I think we served in a war together. I also believe that the reason he takes care of me is because of an agreement we made. I also believe that he does it because he enjoys doing it. More than anything, I believe that Michael does it because that's what he was created to do. He was created to Love, just as we all were. However, I think that he understands that a little more than any human really can.
I see him sometimes. Not too often. I usually just talk to him, but not out loud, of course. No reason to scare the neighbors. He delivers my prayers for me and helps me to relax. He does a good job of keeping me safe and he helps make my life less stressful. He also helps me with my projects. I have a lot of metaphysical projects going on, and he upkeeps a lot of that for me. Plus, he helps me with MY angel duties. Most of all, Michael helps me to understand what is important.
He helps me understand that Loving is paramount, and fear is an illusion.
Next time you talk to your angel, give him a hug. They enjoy those more than anything. :)
Love and Prayers, Shay