358/2 Days Confusion with "Days 256-258: News"

I just saw the cutscene where Roxas, who is on Destiny Islands, sees Xion(?), and then reality warps into that cutscene from Chain of Memories (with Riku and Zexion). What happened? I'm so confused! Roxas turned into Xion, Riku, and then Sora? Then, Roxas was seen running elsewhere in the background, and he later says that he saw someone who looked like Xion. So, was that Xion in the beginning who looked like Roxas? Who did Roxas see? Someone, please explain this to me!

 

i haven't even played the game yet but i know this
sora started to remember all his friends not just kairi and that made xion(who is made up of sora's memories)change into different memories.
also xion takes the form of the viewers connection to sora

 

So does that mean that Xion was Roxas in the beginning of that cutscene? Also, Sora has never seen or known Roxas, so should Xion actually be able to turn into Roxas? And what of the Chain of Memories cutscene that Xion saw? Sora never saw that. And who did Roxas see that he said looked like Xion, and why can't he remember what happened that day?

 

It was all a freaking nightmare Xion had, because she does not know her identity. That's all. If you haven't finished the game, keep playing it. You'll understand what Xion is. And I can't answer the question about Riku unless you want to be spoiled.

 

Spoil Me. and use

Spoiler

tags just to keep everybody else happy :)