Some quick questions.

I can find 2xC and 1xF on the dates I want to get to FRA-MCO and back.

Ideally I would like 3xC but what I think I will do is book the 1xF and 2xC and change the F to C if another seat opens up later.

I assume that there will be no difference in tax between an F or C redemption so I would be looking at getting a good sum of miles back in return.

Can they just change the F redemption to a C redemption or do they need to cancel and rebook?

If it's a cancel job do they need to cancel all the tickets and rebook or just the F ticket?