no.. not at this time
No
you can download songs online and insert it to your guitar hero game. search how to download songs to guitar hero two.
You can't download songs.
No
No, Guitar Hero 3 has no DLC, if you wanted to put new songs on it you'd have to hack it somehow. The new Guitar Hero: World Tour will have DLC though, you'll be able to download songs onto and play songs from your SD cards (they will probably let you download all the songs from the previous games). If you want more info on Guitar Hero: World Tour for Wii check out the Related Linksbelow.
It depends if the Guitar Hero 3 songs were released as DLC on GH: World Tour. There is no way to directly import songs from Guitar Hero 3 onto World Tour.
If by guitar hero 4 you mean world tour the answer is yes. go into the xbox live marketplace and look around.
nope
you cant
NO
no
You can't. You can only download songs in Guitar Hero III for PlayStation 3 and Xbox 360. However, Guitar Hero World Tour, 5, and Warriors of Rock support song downloads for all consoles. But Rock Band has way more downloadable songs, so that might be a better option.