When exactly does the Child Timeline start?

Hyrule Historia made the split timeline official, but there is still one aspect of of it that is unclear and that's how much of the Child portion of OoT still happened?

Most Zelda theorizing videos on YT seem to be operating under the assumption that on the Child Timeline none of the actual events of OoT still happened besides in Link's memories.  But I find that unlikely for a few reasons.

1. The Great Deku Tree still died, since I think it's unlikely he's simply off camera in Twilight Princess.  That should have been prevented if Link was sent back far enough to undo all of the problems Ganondorf caused.

2. Link having Epona in Majora's Mask.  A common assumption seems to be that Link's relationship with Malon had to start over from scratch, that he just shows up at the Ranch as a stranger going "you don't remember me but we had a thing in the future so can I borrow your favorite Horse?".  I really think everything up to Link first being taught Epona's song must've still happened.

3. I've also seen a common sentiment that Ganondorf's imprisonment and attempted execution in the Twilight Princess flashbacks is some Minority Report type situation where he's being punished for what he could have done but didn't actually get to.  But I really don't think that much moral ambiguity is the intent of the scene.

4. And Skull Kid remembers Link teaching him Saria's song in the Lost Woods.

Clearly a lot of Zelda fans like the pathos of Link being in a situation where no one he helped remembers him at all, especially to explain the mood of how Majora's Mask opens.  But the opening of Majora's Mask explicitly tells us this is about him missing Navi, that's the only angst necessary to explain it.

There is a recent fanmade animated project on YouTube that depicts Link as being sent back to exactly when he first pulled the Master Sword.  There is a lot of logic to that mechanically, that's when Time started being messed with so that should be the furthest you can reset it to, and if Link went back any further he'd be stuck inside a locked Room of Time.

The problem with that theory however is the ending scenes of OoT seem to show Link going right to the place he first met Zelda when her and Impa should have fled the Castle by that point.  But I suppose there are ways around that.  

And that initial opening of the Door of Time still happening perhaps best explains why the Triforce pieces still splits up.