A. The US policy is that a nonrefundable tkt may be applied towards an unrestricted ( refundable ) less the 100.00 change fee at the time of change. The new ticket will take on the non refundable rules, but subsequent changes may only result in a fare difference based in the changes made to it.
i.e. you are only hit with the 100.00 on the initial change, but if the new refundable is a 3 day advance BA3US ad you make a change without 3 days notice...then you pay the difference up to B8US or whatever.
This policy changed not to long ago. Travel agents are still calling for clarification because there used to be a waiver associated to it..not required now. So it appears that the above scenario would actually be a valid work around, but where to find an unrestricted fare that's about $400...?