It might be "MILANY", as in: He is a "Milany" guy; But, it wouldn't be a "proper" adjective. The proper DEMONYM or GENTILIC would be: MILANESE, or MILANIAN, or MILANER. And I think that MILANESE is the most widely used.
If you were from Milan you would be a Miliani
The proper adjective for Portuguese is "Portuguese."
The proper adjective for southwest is "southwestern."
The proper adjective for Haiti is Haitian.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Siam is Siamese.
The proper adjective for George is Georgian.
The proper adjective for Georgia is Georgian.
The proper adjective for Mayan is "Mayan."
Freudian is the proper adjective for Freud.
No, old is not a proper adjective. A proper adjective is an adjective derived from a proper noun, such as Swiss cheese, Bolivian pottery, Chinese silk, etc.
France is always a proper noun it is never a proper adjective (what is a proper adjective? The adjective is french. I like french food
The proper adjective for Antigua is Antiganantigan