Yes you can buy them separately. At least in Rock Band 2 you are able to.
First turn the guitar on and then connect it to the wireless receiver
yes it does
No
Yes, at RedOctane.com
Yes any guitar is compatible with any game
Yes, It can
yes it can all guitars work with all games on the 360.
I am not sure but I know you can create songs on guitar hero world tour. I was searching for the same question. I also know that you can download songs already made at the playstation store. (playstation store/addons/disc based games/guitar hero 3)
Guitar Hero World Tour is certainly considered one of the best Guitar Hero editions. It is available for the Wii, XBox 360, and PlayStation 2.
If it's the playstation 2 version of world tour then yes it should work perfecty well, if not better than the wireless controllers!
No, Rock Band 1 was released way before Guitar Hero World Tour so the drums aren't compatible. Also the guitar hero world tour drums have cymbals and the rock band doesn't. In the end: You can't back track.
If you have the one that plugs in through the USB port then it might work.