You'll need to give proof of that one. Can't exactly hold an argument of someone being strongest when he gets off'd.
Correct.
I'm normally somewhat versed in the different inteviews and I don't remember Nomura stating anywhere that Xemnas is the strongest in the universe.
If he would be, he would not a) get his ass handed back to him everytime he faces either Sora or Riku and b) he would not be MX's bitch. ;P
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As for the hearts though it should be obvious what happens to them if the Heartless are felled by a Keyblade:
If no Nobody is present, the heart is reunited with its body and the original entity from which the Heartless was originally born from will return.
If a Nobody is present the heart will fall into a state of suspension until the body and soul are freed as well.
One of the primary reasons Yen Sid and Mickey were so insisting on the Organisation being destroyed completely was because they were holding millions of hearts captive in their forcibly created artifical Kingdom Hearts, preventing those hearts from returning to their true form.
And for that, I
have proof from both Nomura interviews and the games themselves, namely Re: Coded:
358/2 Days Ultimania said:
-- The last thing that Xion asked Roxas was to "Set free Kingdom Hearts." Was this due to Sora and Kairi's memories?
Nomura: Yes. At Xion's core are Sora's memories. And so what he felt, that the world's order should be maintained, she also felt. But Sora doesn't know anything about the Organization's plans yet, so strictly speaking this is not exactly Sora's feelings. The hearts freed from Heartless must return to where they came from, but if they are captured by the Organization they will not return to the body they are supposed to, so it is the same as if the Heartless took them.
Nomura is normally pretty vague when explaining things, but it doesn't get much clearer than the bold part.
So, now we've taken two journeys. One to stop the darkness from spreading, and the other to put all the lost hearts back where they belong. To tell the truth, neither one was easy, but I sure was glad to be the cricket to write down what happened. Two journeys, both sittin' quiet right here in these two books.
Jiminy reminisces about the bigger goal of KH II here as well. While Sora's primary
personal goal might have been to find Riku and bring him back home (just like Donald's and Goofy's goal was to do the same with Mickey), the goal on the
universal level was to prevent Xemnas from getting his god-like powers and free all the hearts the Organisation had captured to make their KH from.
KH III also seems to run on such a duality storywise. The more personal goal is to save those who are in torment (primarily TAV, Roxas, Naminé, Xion and Ansem the Wise. Eraqus and Isa are optional as they're not mentioned within the original list) while the goal on the universal level is to stop Xehanort from destroying the universe with his crazed crusade to unleash a second Keyblade War and prevent a repeat of the past where darkness covered nearly everything already once.
