These World Tour instruments work find with RB2 so yes they should work with RB Beatles as well. Compatibility Chart: http://cdn.guitarhero.com/ghhub/GHWT_compatibility.pdf
I don't believe so. Rock Band and Guitar Hero instruments don't play nice together because of all that jazz about being competitors and all. I HEARD some of the newer versions of Guitar Hero would be able to play Rock Band games too but so far it's only been a rumor. Sorry.
This one won't. You have to buy the one specifically designed for the Wii (the Wii version also requires that you put in a Wiimote for each instrument being used... actually annoyed me so much I bought the 360 just so I wouldn't have to change out the wiimotes anymore :)
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