Worlds' Finest #0-Near Mint (9.2 - 9.8) Alternate Reality Versions of The Characters

It's the origin of Supergirl and Robin on Earth 2! How did their first mission on that world affect their situation as Power Girl and Huntress today?
(NOTE: 1st appearance of Power Girl as Supergirl;
1st appearance of Huntress, Helena Wayne, as Robin)