Noble titles in the age of same sex marriage and gender reassignment

Factual Questions
21

The Queen is the Duke of Normandy in her own right;

However I don’t think that makes Prince Phillip the Duchess of Normandy.

22

And, appropriately, Lord of Mann.

23

Furnish doesn’t get to call himself Lady but it turns out that he’s listed as mother on the birth certificates of his and John’s children: