That being said, Austria will certainly recognize as official all titles from reigning monarchies: as such, Archduke Lorenz of Austria-Este is rightfully acknowledged as a prince of Belgium (with the qualification of Royal Highness). I believe that's how he's styled on his Belgian passport -- correct?
Is it true, however, that in Germany one is allowed to style himself with the name of a formerly reigning or mediatized house, but without any princely or ducal title -- let alone the qualification of (Royal) Highness? Is the present head of the house of Wittelsbach styled, on his German passport, as "Franz von Bayern"? After all, he is legally a private citizen, since the dynasty got deposed a century ago.
If so, I'm assuming that his cousins likewise can style themselves as "Georg Friedrich von Preussen", "Alexander von Sachsen-Gessaphe", etc. Correct?
Are at least noble titles legal in Germany, however? Can one style himself as a count(ess)?