I believe you can, yes.
Guitar Hero World Tour is Guitar Hero 4.
Guitar Hero World Tour and Guitar Hero Metallica
yup
No
NO
You can play Rock band with a guitar hero guitar, but you can't play Guitar Hero with a Rock Band guitar.
Yes, the controllers can be used for all guitar hero games
yes
Yes. You can play any guitar hero game (including Band Hero) with any guitar (including the Guitar Hero World tour guitar.) As long as the game and the instrument are for the same video game console.
You Can Play With just guitar as there is a solo guitar mode
no, each game has a different song except for guitar hero smash hits
The same way you play with a GH3 guitar