beat story mode for goku and then go to extras mode and all the red doors should be open
After the 19th island, Red Dragon (June, 2011), the 20th Island is Shrink Ray Island, a miniaturized adventure, on July 28, 2011.
ooh dragon fable! what else hello kitty island adventure? >.<
Listen to Basho.
You don't need to worry about that.
magic
You get them when you complete your Ninja Training. (see related question)
The Island of Adventure was created in 1944-09.
The yellow and blue dragon is from the children's book "The Snail and the Whale" by Julia Donaldson. It is not about an island with crocodiles and lions, but instead follows the story of a snail who hitches a ride on a whale's back and goes on an adventure around the world.
there is no magic dragon island
When you do all of that stuff you earn the claws from Basho
Super Adventure Island happened in 1992.
Adventure Island II happened in 1991.