Someone please explain to me the whole deal with Xion and Roxas being a replica

[Hoarse_Phuqer]

So I know that by the game's logic, you need a heart and an empty replica to make near perfect people. My question is that how in the hell did Roxas came into being since the empty replica was at Radiant Garden late in the game and Roxas' heart was resting inside Sora throughout the whole journey. I for one don't recall Sora being made aware of this, or him going to Radiant Garden to have Roxas' heart transplanted into the vessel. How then is it that Roxas shows up at the Keyblade Graveyard when, to my knowledge, his heart was still trapped inside Sora?

As for Xion I admit I am a bit rusty in my KH lore, but in the end of 358 Days, Xion went back to Sora, right? I assume that the Xion that fought at Xehanort's side was brought from the past using time travel shenanigans. But the original Xion was still inside Sora's heart, so did she just like take over the body of the past Xion Sora had been fighting in the Graveyard? I'm so freaking confused right now...

As for Namine, she was still in Kairi's heart all this time so I assume that at some point Kairi went to Radiant Garden to restore Namine, but she is nowhere to be seen when Namine wakes up. Not really confused about this but it sure was a damned missed opportunity to have them interact.

 

[rac7d]

I dont know how they came accros Xions hearts I assume it was in sora
then roxas heart traveled to radiant garden and roxas beamed back to the graveyard in an instant

but they needed bodies vexen made some

Time travel is sucha cheat

 

[AdrianXXII]

I was under the impression Xion in the Org was a new Replica that the old one slowly took over upon the confrontation.

My guess was that the whole experiment about recreating a heart from data that Rikunort was going on about was in regards to Xion.
I dont get how Xion's heart transfered out of Sora, with both Roxas and Ven we saw it happen, but not with Xion so it's a bit weird.

I'm guessing Ienzo and co. did something similar for Roxas, recreating his heart a bit from data. Though how his vessal got a Org coat and to the Graveyard is a mystery.