get it from amazon.com
Don't know about SSJ4 Goku but the intro of G.T is a Japanese song called Dan dan kokoro hikareteku
Shenron took goku (in kid form) when pan (his granddaughter) was very young. 60 year's later goku and vegeta's great great grandsons were fighting in the world martial arts tournament and we see...
no.
Nope. The best you get is Super Saiyan 4 Goku (who's more than awesome enough, so it's fine).