The Guitar Hero III guitar is completely compatible with Guitar Hero: World Tour provided you're still using it with the Wii.
Yes the guitar hero world tour (4) controller will work with guitar hero 3 on any system
no because u can't play the drums on guitar hero 3
yes it will for both
Yes
Yes, the original guitar works for all of the new releases (so far) including rock band. But, the world tour edition is much sleeker, with the joystick closer to where your hand should be, and a star power button.
yes; and I'm not making it up
yes
Yes, the guitar controller form Guitar Hero 3 is compatible with Guitar Hero 4 (World Tour). Just turn on the wii-mote in the guitar controller and it should recognize it in the game. Keep in mind that only one player can be the guitarist and the other has to play the bass guitar. Hope this helps... have fun and ROCK ON!!!
yes
Yes they will work
Yes, It should.
I think they only work with Guitar Hero 4