First of all I would like to note that I anwsered these questions going on two Angel mediums I know and a few courses concerning Angels so please don't take anything here as absolute truth ^^;
1: Well Guardian angels work much like spirit guides, they can help guide you and offer warmth, they can comfort you when you need it. Protecting you goes beyond the physical meaning.
2: Angels don't hate, in fact as far as I know they are incapable of any negative feelings, they are angels, beings of pure warmth and light and just like spirits guides they will always work in your best interest.
3: I don't think so, you are pretty much stuck with the one you're given.
4: Now this I really don't know, I wouldn't be surprised if they pick us, or maybe its like with spirit guides and we get the ones we are meant to have.
5: You can contact your guardian angel through meditation and dreams yes.
Hope this helps.
"If you take a copy of the Christian Bible and put it out in the wind and the rain,
soon the paper on which the words are printed will disintegrate and the words will be gone.
Our bible IS the wind and the rain."