Hand, Backpack, Charity

[alexperience]

Hi all, I'm not incredibly new to Munchkin having played a few times, but I would like clarification on a few things:

At the end of your turn you are allowed to keep at most (unless otherwise specified) 5 cards in your hand. You would in theory keep cards you don't want to lose easily or that you don't want other people to know about.

If you have more than 5 cards,

1. What exactly can you put in your backpack that you are not carrying (tapped/turned sideways on the table in front of you?
2. How many things can you have in yoru backpack? What are the restrictions?
3. Can you put monsters in yoru backpack?
4. Are there any restrictions about trading with other people?
5. Can you please clarify the restrictions for getting rid of Big Items?
6. And lastly, during the charity phase, whatever does not get "played" goes to teh person with the lowest level, unless that's you, then it is discarded. Does that person get everything you're going to discard or only some items?

Thanks everyone. I know that's a lot of questions!