Solhunter

Sadly, I missed the NHK program. Guess I'll just have to wait until it's archived unless someone on Youtube recorded it.

Actually, it was Present Sol that she transported back into the past to fight against his past self. After the battle, Sol was transported to the present timeline and wondered if he had returned to the right time period. It also depends on how Time travel actually works in GG because as That Man told Sol in one ending(where Sol presumably dies along with Order Sol), having his past destroyed shouldn't have any effect on his present. Meaning that phenomenon like the Butterfly Effect may exist in GG. So, Order Sol likely still exists in another timeline.

Seriously, Daisuke said a couple of months ago in an interview that all of the characters from the past games are getting in, just not all at once. Like Blade said, it isn't a matter of "who gets in, who's left out", but "who's coming next depending on story importance". No one's being left out.

No, because Valentines are imperfect Gear-like constructs created from Justice's DNA by the Universal Will/Merciless Apocalypse back in 2074. Valentines are essentially clones of a clone. Being a clone of Aria does not label you a Valentine. Dizzy is also confirmed to be a Copy/Reproduction/Back-up of Justice by both Crow and Paradigm, though no one knows where she came from.