can some one clear these questions up? [series/ending spoilers]

So I've finished every kingdom hearts game to date (except for the original coded for the cellphones) and this is the only game that actually confused me. Hmm ok where do i begin... these questions have no specific order its just the order i thought of the questions.

1)Both Riku and Sora were sent to the sleeping worlds the unlock the sleeping keyholes but then Riku ended up in Sora's dream?
b) I don't get it, how did Riku end up in Sora's dream?
c) If Riku was in Sora's dream, how come he could see Sora in The World That Never Was? (before you fight anti black coat)
d) I thought they were just being sent to worlds clouded in darkness (resulting in a sleeping state)

2)So master Xehanort (from the past) was the master mind behind the whole plan?
b)How did he even know he was going to have future incarnations of himself
c)How did he even know about Sora and Riku
d)How did they all time travel? (with all the rules because it really confused me)
e)So they all went back to their original time? I thought they can't go back into time? or change anything that was suppose to happen.

3)What was the point of making Sora and Riku younger? from other theories its because thats the age they would have been from that point in time that the world was sleeping in but Terra/Ven/Aqua/Roxas/Xion all look the same and they're all from different periods in time.

4)Maybe I forgot what happened but was there a point to showing the other Riku inside of monstro? he showed up for one scene and that was it.
b) same with Vantias, when I saw him in the trailer I was hoping you would be able to fight him,

5)Why doesn't Namine look exactly like kairi? the reason roxas doesn't look like sora is because of ventus. is there any reason why namine is blonde?

6)So if you're recompleted by having your heartless and nobody destroyed, doesn't that mean master Xehanort has been recompleted too?
b)why did he have to come back from the past? (assuming that he did because he disappeared with the rest of the organization 13
c)what does this mean for terra? maybe hes one of the new organization 13 members?

8)So the mysterious figure in birth by sleep was young Xehanort?

7)Anyone else kinda wanted to see Sora become a vessel? maybe the beginning of kh3 you have to save him (Kind of like the beginning of kh2 where you have to play as Roxas)

Random thought: This game kind have killed the uniqueness of the keyblade.. it seems like anyone can just have a keyblade now. I mean it's not new knowing Kairi can wield one (which was really random when it happened in kh2 and then she never used it again) but now Lea has a keyblade? In the first game it was said the keyblade chooses its master (made it sound like there was only one or two) which made it sound unique like you had to be special or destined to have one, but now ever since bbs (still a good game) you can now pass down keyblades and it seems like anyone can have one?

Also I really don't like how the retcon'd the fact that nobody's can actually have hearts without the use of kingdom hearts, it kingdom of kills half plot of kh2 (exaggeration but still).

Other this confusing and questionable direction the series is going, i still love the series and going to see it to the end. hopefully someone can help clear up my confusion! thanks.

we'll that certainly does clear things up, thank you!

I'd chalk Sora looking older due to some dream thing.

I'd say Young Xehanort battling Terra, Aqua and Ven doesn't look like it could fit into the BBS storyline but one could always imagine Young Xehanort was around in the shadows due to his time travelling.