Hello, in that case, would Solo respond with 2 separate (counter)-attacks?

Yes. In this case Han would attack before AND after Greedo shoots, making all necessary assumptions of course.

Possibly. There are plenty of different ways the exchange could go, and in one of them Han Solo would get to Return Fire.

Han would not Return Fire for example if:
- Greedo is defeated from the attack from Slow on the Draw. After Parting Shot Greedo is removed from the map, and there is no valid target for Return Fire.
- Greedo is not defeated from the attack from Slow on the Draw, and Han is defeated from Greedo's attack. Han is removed from the map, and would not Return Fire.

Until your opponent gets smart and places greedo in a way there is no first shot and no return fire.. ugh