Beware of unmarked spoilers
Harley, who swears a lot, is the alternate (and Race Lifted) version of Marvel UK's character Motormouth.
Confirmed - we get her full name in #3, and there's a Motormouth + Killpower poster on the wall. In this world, they seem to be musicians. And in the final issue she gets her wounded throat repaired with cybernetics, bringing her closer to her Earth-616 counterpart - although this time it's Tony Stark, not Julius/Killpower, who saves her. The Hydra attack was a False Flag Operation arranged by the British Prime Minister.
Confirmed - in Captain Carter's world, Hydra hasn't even existed since the 1940s. The "Fantastic Five" are the Fantastic Four, who have accepted Spider-Man as a member in this continuity.
Unconfirmed. It might be revisited in a sequel, but the first series gives no further detail about the Fantastic Five.