I'll try and answer first.
2) The 40mm can be used on all Canon EOS Digital Cameras - including Full Frames.
A good lens for street photography, especially on a Full Frame.
3) The 40mm is definately the sharpest of these three lenses.
Then the 50, then the Kit lens.
+1. I have never shot the 650D, so I cannot comment on it. It uses the same sensor as the 60D. I have a 60D and I like its ergonomics. You may want to try them out in a camera shop to see how they feel in your hands.
The 40mm pancake is an awesome lens on crop or full frame. For $150-200 USD, it is a steal.