about the origin of ultimecia (big big spoiler)

[Future Esthar]

Let´s even consider that Ulti uses the "absorbed into time" thingy.
And then revives Rinoa.But that would be a time loop.But it didn´t make sence.The loop would had to have a beggining somewhere.Even the one in which Ulti passed her powers to Rinoa had a beggining.

So what if she is even at Edea's house or not?

If she wasn´t at Edea´s house she was not Ulti.Duh.

Ellone also dun fight Ultimecia too, not to forget Xu, the "Queen" in the CC group, the library girl and etc. And they can all be sorceress who knows?

There is no real basis to say that(except Ellone which is Rinoa).
With more accuracy I can show you that Quistis and Selphie were sorceresses.

If Edea's castle is the orphanage you refering to, then let me tell you the layout of the orphanage is totally different from Ulti's castle and there is no way Squall can rememeber anything.

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I believe Edea´s house is a ruin of a part of Ulti´s Castle.