I'm looking as media queries and responsive websites and have three questions:

1. If you have largebgimage.jpg as a background image and smallbgimage.jpg as a background image set in your CSS, will it load both images regardless? Or will it depend on the width of the browser at load time? From what I can see the main con of RWD is that, for mobiles, it is heavy on bandwidth.
2. Is there a guide anywhere that shows support for media queries on different browsers/devices?
3. What's the difference in media queries between max0width and max-device-width?