Post-Flashpoint Earth 2 Jay didn't exist at the time of the Flashpoint event. After the event DC did a relaunch called the New 52 which showed the new DC universe after Flashpoint. Earth 2 was one of the New 52 series.
Either Jay Garrick clarification you suggested would not be a good idea. Wonders of the World doesn't state what comic he's from and "Earth 2 Series" could be misinterpreted potentially as meaning Golden Age Earth 2 Jay Garrick and not Post-Flashpoint Earth 2 Jay Garrick.
Yes, I am referring to the third Kara. The thing is that while they all share the same name of Kara Zor-El and they have all been the main continuity Supergirl, they are very much not the same people at all. Nothing that happened to one of the Karas happened to the other two. While Kara Zor-El (Prime Earth) is technically accurate, I wanted to keep the Post-Flashpoint to keep it completely clear which of the three Karas is meant.
Additionally, both of these versions of the characters were created after the Flashpoint event, so Post-Flashpoint encapsulates the entire published history of these two characters.
Re: F!Jay Garrick (Post Flashpoint Earth 2)/Kara Zor-El (Post Flashpoint Prime Earth)
Either Jay Garrick clarification you suggested would not be a good idea. Wonders of the World doesn't state what comic he's from and "Earth 2 Series" could be misinterpreted potentially as meaning Golden Age Earth 2 Jay Garrick and not Post-Flashpoint Earth 2 Jay Garrick.
Yes, I am referring to the third Kara. The thing is that while they all share the same name of Kara Zor-El and they have all been the main continuity Supergirl, they are very much not the same people at all. Nothing that happened to one of the Karas happened to the other two. While Kara Zor-El (Prime Earth) is technically accurate, I wanted to keep the Post-Flashpoint to keep it completely clear which of the three Karas is meant.
Additionally, both of these versions of the characters were created after the Flashpoint event, so Post-Flashpoint encapsulates the entire published history of these two characters.
https://en.wikipedia.org/wiki/Flashpoint_(comics)