On Poptropica, you can only beat an island once to receive credits.
But you can play an island over again by opening the small map at upper right and selecting "restart island" (blue button).
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
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
You can't. If you leave without finishing the game, it stays completed. Once you beat the game, there is no way to come back through the portal to it.
The only monsters to beat with a bomb are on Astro Knights Island. (see related question)