(See the related questions for each of the three planets, and for the final battle on Mordred's asteroid.)
all you get is the island medallion and 100 credits
The 9th Island was Astro Knights island released in 2009. (see the related question)
well just beat the stupid thing ingnore her baby birdies
On Astro Knights Island, there are four "boss" robots, one for each planet and the final battle. This arrangement is similar to that of other video and computer games. You must beat all three planets to reach the final battle, because you need the three space knights to get the Golden Key that leads to Mordred's lair. (see the related questions for solutions)
Wimpy Wonderland Red Dragon Island Counterfeit Island Mythology Island Astro Knights Skullduggery
well just beat the stupid thing ingnore her baby birdies
you jump over it
Defeating Mordred and his warrior suit wins the island, and you receive the Island Medallion and 50 Poptropica credits.
Only by telling you how. (see the related question)
There is no easy way. (see related question)
no, there is not
The only monsters to beat with a bomb are on Astro Knights Island. (see related question)