Oh dear, lots of things to reply to.
Just seems like a fannish "neat idea" based on the fact that in OoT, Link and Zelda as kids look vaguely similar to each other, which they really don't that much if you look at both in-game models and official character artwork for the game.
That is preciesly what my "theory", which would more accurately be called "wild speculation" is, a neat idea based on some flimsy evidence. What gave me the idea was
not chiefly the similarity between Zelda and Link. I will point out that the entire Gerudo population is composed of the clones of three women. Plus there are those two guys who are always arguing, they look like twins but most certanly are not. What gave the idea was chiefly the backstory of both the Civil War and Link's mother. The fact that Zelda's mother died during the war, and Link's mother showing up in the Lost Woods, grieviously injured and with an infant in her hands. It got me thinking that perhaps they were one and the same. Of course my evidence would not hold up in court, hell I wouldn't even
get a trial with it.
There's the problem that if Link is sent back, then everything he did as Adult Link would have been undone and Ganondorf would be free from the Sacred Realm
One would assume that Link has faith that his past self, currently resting in the heart of the Temple of Light, will be able to beat Ganondorf. Hell, if he is a strong believer in destiny then he is dead certain that the fact that he exists prooves that his past self will emerge victorious. Of course we know better.
I know, it just seems improbable that if their objective was the queen that they'd let her go so easily, unless they were possessed of an extreme paranoia about the forest.
Or they merely wanted the Jewels and pretty stuff in her carriage and weren't the least bit interested on whether she lived or die provided that she did not interfere while they were busy looting.
So this particular jump in time created a change in universe, but the innumerable other times it happened in Ocarina of Time, Oracle of Ages, and Majora's Mask did not?
Besides, the multiple universe idea is bunk after Master Quest. In the Spirit Temple in Master Quest, Link hits a switch that drops a chest into a room he can't get at as an adult. When he goes back in time, that chest is still there. The conclusion is that parts of various sacred areas are immune to time. This supports why Zelda sent him back in time- the Sacred Realm is immune to time, hence it was safe to send him back, since Ganondorf would always be sealed away. Until Wind Waker, anyway.
This fits pretty well with my
Multiple Sequencial Universes Theory of Time Travelling. You see the use of the word "Universes" is somewhat misleading. I came-up whith it in order to wrap my mind around the time travelling issues that Harry Potter 3 brought up. Esentially "Universes" does not refer so much to the physical stuff in the world so much as the people, specifically the time travellers. It is very hard to explain, but the "Sequencial" thing is very important to the theory.
The pulling/ replacing of the Master Sword happens after Young Link enters the Sacred Realm. Once Adult Link left the Sacred Realm, wouldn't he see the second Master Sword when he left, assuming we stick with the multiple universe theory?
This may actually require that I use more traditional Multiple Universes explantion instead of my version, which is so convulted I can't put it into words. Link is from Universe A. At the end of the game he leaves A and enters Universe B. The Master Sword does not go with him. So A's MS stays in A and B's MS can be seen in the pedestal where it is supposed to be. So when B's Link awakens, there will only be one Sword, the one stuck to the pedestal.
Alternate timelines don't work, because you're essentially creating a world that is identical to the original Hyrule except for one minor detail at the point of divergence. I'm sorry, but no mere mortal is going to be able to do something that rivals the Three, especially not without the complete Tri-force.
Time travelling does not creat multiple universes, they already exist.