Ok, I have done some progress:

@1: Still not clarified. I will open another request with my code.

@2: I accepted that there is no way to select a locale that has a leading zero so I have to work on every locale as soon I try to add a new language.

@3: For this problem I advise the solution of Bruno Cerecetto in the request day incorrect in angular material datepicker. That worked for me.

Best regards

Parascus