no
Someone
Me! Lawlawlowkozl
There is no dungeon called final island, if you mean western cave then the answer would be mewtwo
48 floors
It's the Darkrai battle, as also seen in Pokemon Mystery Dungeon Explorers of Time/Darkness.
48 flloors
not sure maybe mew?
48 floors
after you beat the final boss
it depends it could range from 10 to 50 or even 100
There are 50 floors.
After beating the game it becomes available for purchase at Wigglytuff's shop