When an opponent plays this card and flips over a support:

A) Can he place the development in any zone?

B) If he targets me, can he play my support face-down as one of HIS developments?

Based on the wording, which says nothing about moving the card, I'd say it's a straight flip on the spot. Whatever zone it was in, that's where the new development pops up, so to speak.

This is apparently not the case.

From Lukas at FFG:

Q. If I target with Rodrick Riders effect some attachment on my unit like Disease or Hex, where the development from that attachment goes? To my zone or to it's controller coresponding zone? Or elswhere?
A: You cannot control cards as developments that are owned by your opponents. So once the attachment tries to become a development in your zone, it is immediately discarded from play. This will also be updated in the next FAQ.

This is an interesting new concept. I have always played it as the 'Support' becomes a 'Development' in the zone it was in. This will make a bit of difference if it becomes an official new rule. I think the reason it never came up before was, because 'Development' moving cards always moved to other zones in the same capital. Note to me:- Must remember that my opponents 'Developments' cannot be in my Capital. Cheers!