Maybe I can answer some of your questions ;o).

Aiko has been around since Vicky 1 or 2 IIRC and the first gen was a morph of the original Stephanie figure (who was in turn a female version of Mike 1 or 2 I believe). Hiro definitely didn't make an appearance until the gen 3's.

The Girl was a standalone figure that came out during the gen 3 iterations.

Stephanie Petite 3 and David 3 are based on the gen 3 figures.

SheFreak was based on Vicky gen 3. I can't remember if the original Freak was based off of Mike 2 or 3. It's 3 I think, but don't quote me on that one ;o).

That's all I can remember off the top of my head...lol.

Laurie