Kingdom Hearts II Speculation On Unexplained Events and Questions In The Series

So after some research I came up with a list of "plotholes" within the series that are still unresolved/unexplained. What I was wondering is:
1. Will these ever be explained?
2. Did I mess up somewhere and present something explainable as a plot hole? If so, please provide evidence

Plotholes in Kingdom Heartsssssss

KH
How did Sora, Riku, and Kairi learn of the existence of other worlds?
Who was the voice speaking to Sora in the Awakening?
How did Ansem, lacking a corporeal body, write some of the reports?
Why did Tarzan recognize Hollow Bastion?
How did Ansem manufacture the Dark Keyblade?
Where did Soul Eater come from?
How did Riku know how to travel within the darkness?
How did Kairi hugging Sora restore his heart?
How did Kairi end up at the End of the World at the end?
How were Riku and the King inside the door?
How did Sora, Goofy, and Donald end up on that sunny green crossroads?

Chain of Memories
If Vexen could create a fake heart, that acted much as a real one, why didn’t he make ones for the other members?
If Naminè shattered the Repliku’s heart, killing it as stated, how did it come back?
Why did Sora lock Floor 13?
Why did Vexen need to die if Marluxia simply could’ve had Naminè erase the memory of whatever Vexen said?
How did DiZ get Riku to Castle Oblivion from inside the door?

KHII
Why was Riku able to summon the Guardian?
Why was Ansem remaining in Riku’s heart never touched upon?
Why is there no true proof that the boy on the beach was Roxas?
What did Xemnas mean when he said “Or maybe I’m all there ever was?â€
If Riku took off his blindfold why did it come back when DiZ’s machine exploded?
How did Naminè and the Organization learn how to hack DiZ’s system?
Why didn’t Sora starve to death?
Why was CoM described as “things happened†when it is relevant to the plot?
Why did the majority of Organization XIII not appear evil?
Why did Sora flat out murder Luxord and not the others?
Why did Riku return to normal when the machine exploded?
Shouldn’t the Nobodies on the ground when KH exploded have received hearts?
During the final battle, Xemnas absorbed and united with KH, by killing him didn’t Sora and Riku harm KH?

 

Some of those things HAVE been explained... Not many...but some.

Sora, Riku and Kairi knew there were other world's because Kairi is from another world (Radiant garden) Riku even says so, that he would never know about these other worlds if it hadn't been for her.

"Ansem" wrote those reports before turning heartless I think...

Riku learned how to travel in darkness from Maleficent didn't he?

The Vexen thing has always confused me to. :p For a scientist he's really stupid...

 

Riku was able to summon the guardian because he gave his heart to the darkness so he could have the strongest power. This is also the reason why he looked like Xehonart's heartless. In the first game he got the power of darkness. He just released it in the second game because it was his last hope at winning against Roxas.

 

A heart is a rather complicated work. Vexen may have been able to create one with long {so we assume} hours. And it's likely that he never bothered since he assumed that Kingdom Hearts would return the hearts.

Marluxia could have had Namine erase the memory of what Vexen had told Sora BUT killing Vexen would have provided an example to the other Nobodies in Castle Oblivion. Basically, 'You don't follow me you can be killed.' Sort of sad Axel set Vexen up for death but I'm sure Axel felt nothing about it.

Anyway...The boy on the beach is Roxas. Xemnas doesn't say it outright but he strongly hints at it. 'I have met him.' 'He is a lot like you.'

Organization XIII did not appear outright evil perhaps to appeal to Sora that gathering hearts for them {killing the Heartless in other words} was not a bad thing. Sora is rather weak in the fact that he helps others and Organization XIII preys on such weaknesses. They were more like anti-heros in a sense?

 

Q. Why did Vexen need to die if Marluxia simply could’ve had Naminè erase the memory of whatever Vexen said?
A. Marluxia wanted to get rid of Vexen because they were simply annoyed with Vexen and his personality.

Q. If Vexen could create a fake heart, that acted much as a real one, why didn’t he make ones for the other members?
A. The members of Organization XII wanted to become complete with their original hearts. Making fake ones still makes them incomplete, which is not helping their ambition.

Q. If Naminè shattered the Repliku’s heart, killing it as stated, how did it come back?
A. It is implied that a person with a REAL heart would die if their heart collapsed. The Riku Replica had a FAKE heart. Namine shattered his heart but it didn't affect him because his heart wasn't even there. Another thing is probably because Vexen doesn't really know what it was to have a real heart, he didn't know how to make one in the Riku Replica.