CC4 is for creating characters. Iclone for animation. Headshot for facial captutre / animation. I think the rest are self explanatory.
You use 3Dxchange to port DAZ characters into Iclone. All the information on getting started is on the web.
No is the answer for porting character creator characters back to Daz. The question has been asked a gazillion times in their forums. Again, all the information is on the web.
If anyone has any more input or wishes to correct me please post here.
You're very welcome 🙂