Scottish is the proper adjective for Scotland.
Scotland!
The proper adjective for Wales is Welsh.
Scottish or Scots can be used to describe something of or from Scotland. Scotch can be used to refer to food and drink of or from Scotland.
The proper noun for the adjective Scottish is Scott, for example My father was a Scott. Proper nouns and adjectives must be capitalized.
The proper adjective for southwest is "southwestern."
The proper adjective is Haitian.
The proper adjective for Portuguese is "Portuguese."
Stornoway is an island town in Scotland. The proper adjective could be Stornowayan, which would also be the noun (demonym) for a resident. Adjectives that describe the location might include picturesque or historic.
Vietnamese is the proper adjective for Vietnam.
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.
The proper adjective for George is Georgian.
Mayan is itself a proper adjective.