[Sirch]

Huh? So you think Naruto is the Fourth because of his appearance and skills then you say there was no Fourth to begin with. I'm confused as to what you are trying to say.

I suppose it would be plausible that the jutsu the Fourth did to seal the Kuuybi didn't in fact kill him but instead reverted him back to an infant without his memories or knowledge. But, not likely.

only Naruto and Ero Sennin can do the Rasengan

Spoiler:

I believe that Kakashi did the Rasengan.. or atleast formed it in his hand when he was teaching Naruto about the wind elemental Rasengan. So, it's not some kekkei genkai jutsu that ony Jiraiya or the Fourth can do..