I don't know how much of this is known already, but I will cover everything.
I was upset by the fact that there is nothing we can do about the Jabu blue warp, so I started to mess up with it.
The first thing I came up with was dying while reaching the edge of the blue warp and then getting revived by a fairy. What happens is that the game tries to push us to the warp for let Ruto start talking, BUT we can fully control Link, use items and save. If we stop moving, we get teleported back to the warp. There are also some interesting side effects, like being able to push Ruto and move while we are being teleported away, but I won't get into details since that didn't lead me to nothing useful.
Then I decided to pull out a bombchu and let Ruto start talking to me while being at low health, so that I could die on the same frame where I would be being teleported away, same as you would do with any cutscene skip/wrong warp. After so many tries, I finally got it, and the results were.. interesting.
My last cutscene watched was the Title Screen one, so this might be a possible? wrong warp, since we can't do a cutscene skip here.
If we decide to save and not continue, we spawn back in Jabu without the Sapphire, and everything looks normal. However, if we choose to continue, we appear in.. the Big Octo cutscene, inside Jabu.
We appear on that cutscene, BUT Ruto isn't there, and the cutscene stops just after 'Ruto' stops talking to you and she turns back. Right after that we can control Link, and if we pause WE HAVE THE SAPPHIRE!
We can control Link and move as usual, but as soon as we leave the room, we notice that something is.. different.
For some weird reason we are in a partially loaded - screwed up version of Jabu, where a lot of weird and funny things happen: from black tentacles and partially loaded rooms, to a large number of enemies in rooms, invisible water, enemies which die automatically and a lot of different stuff.
So, this might not be useful right now, but it's quite interesting and funny nonetheless, and with a different last cutscene value or something this might lead to something actually useful.
Here is a Link to the video i made. I would like to have recorded the whole process, but was impossible for me to hit the right frame of death consistently, so I started recording after that; also, I think the setup is really clear after reading.
https://www.youtube.com/watch?v=3ALo5cKOEHkThis is quite a long thread, but I think it was worth, let's see what happens with this!