Those are all very difficult questions, Kostas. I haven't tried it, so I can't answer, but some time ago, Paulie and Ventura started an interesting thread about growing naners in extremely hot climates (very similar to yours in summer, although maybe with slightly higher temps).
You could check the thread out and learn what they found out in a span of 2 or so years.
high temperature banana growing habits
Regarding the frost tolerance. It generally is so, that any commercial variety is almost exclusively less hardy than the popular seeded varieties sold in Europe. You could check out this experiment:
Interesting banana hardiness-project in Georgia
Georgia is in much lower and more humid zone, than Greece, so it will probably help you in one way or another.
And then there are tons of threads like these, laying forgotten in the continuum of this site, popping up each time you search for cold hardiness or drough resistance.
Have a look at these articles, threads... and they might help you. Your climate is very unique and you won't truly know, unless you've found someone who grows naners in your area. What I can say is that I saw edible naners growing, fruiting and thriving in Andalucia without any problems also in winter.
Good luck!