How are Sora and Riku young and had to start over on their training

[Riku-KH]

Here's a confusing question."In kingdom hearts 3D, why are Sora and Riku young in the dream world?
Is it because of Xehanort? Or did Yensid mean what he said and made the heroes start their training from scratch?


If Yensid wanted to train them himself, then why did he send them to a dream world all alone? And I don't mean separated from each other. I know that was caused by Xehanort.


What was the use of Yensid restarting their training if they were just going to train themselves again anyway? It still seems like they were self taught.


He told us why he sent them to the dream worlds, to learn new abilities.
And I guess they were able to teach themselves new abilities without his help.
Was Yensid originally wanting to help them on their journey but Xehanort stopped that from happening?
Why did they have to start their training "with a clean slate?" They were already good. I don't see the reason why they had to teach themselves how to use the keyblade again. Any suggestions?

I suppose this was more than one theory... But they do all relate in a way.

 

[Gram]

Yen Sid explained it early on. He was the one that made them young and sent them back in time to Destiny Islands. From there they entered the realm of dreams.

One dream is connected to another, which means we must choose in
which "Sleeping World" you will begin. I will return you to the Destiny
Islands just before they were swallowed by the darkness and plunged into
sleep. Once dreams take you, you must let them guide you to the Sleeping
Worlds. As there are seven pure lights, there are seven "Sleeping Keyholes."
Unlocking these will both grant you new powers, and free the worlds from
their wakelessness. Complete this task, and return here safely, and I will
name you both...true masters.

Sora's the one that remarks on the clothes. Their new clothes and younger look was also cause of Yen Sid. However Xehanort added the X on Sora's shirt to track him.
It's only by returning to the Mysterious Tower in the present waking world does all that become undone and they return to their older looks.

"Starting with a clean slate" is basically just an excuse to introduce the command system to Sora & Riku as well as giving Nomura a reason to start them over at level 1.
Xehanort didn't stop it from happening but altered the destination. Ansem, as the robed figure, was the link that let Young Xehanort into the dream realm with them and from there YX followed them about trying to tempt one into darkness to take as the 13th vessel. Riku proved no use so they chose Sora.

 

[Davidsawr]

lol kingdom hearts was confusing enough, Nomura didnt have to add inception to it...

 

[wolfshadow]

Yensid also mentioned that even though Sora, Riku, and Kairi (if even for a short moment battle in kh2) were using their own keyblades to the way they wanted to (powers and what not), they were still using the keyblades wrong to become keyblade masters. Basically they were self taught and not properly trained on using the keyblade during battles.

 

[Joker'sHeartless]

I understand where everyone is coming from and I think the confusion comes from Yen Sid's wording.
Even though they were alone in their original adventures just like their Mark of Mastery exam, during the exam they were being guided buy having a specific goal for their powers.

When Yen Sid said "self taught" he didn't mean that they should have had a teacher there with them every step of the way, just that they didn't have any real sort of guidance about what powers they should be developing.

He probably also figured it was too late to make any serious changes to their learning/fighting styles so he simply gave them a lesson he knew would teach them some of the things they missed.

 

[Riku-KH]

Okay. Thanks everyone! I just didn't know what he meant.