1. Check out the Canon Museum: http://www.canon.com/camera-museum/index.html
2. USM refers to the type of motor in the lens. USM lenses can move very fast, and very silent. Some even allow to refocus manually without having to toggle the switch on the side of the barrel. The speed of the lens-motor, and the sound of it are not really connected to the type of the body. With the one exception that if your auto-focus system is not that good, and causes your lens to 'hunt' (trying to focus but failing) alot, then your fast lens will still be slow, albeit still faster then a slow one (being faster in not focusing, doesn't really matter, but hey ;-) ). So the USM lenses should work with all Rebels.
3. My magic balls says it doesn't have the slightest idea.
I hope my babbling helped you at least a tiny bit, and I also hope that if someone spots any errors in it, that he points me at them before they do any harm!
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