Persian
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.
Athenian is a proper adjective for Athens.
Egyptian is a proper adjective.
The likely word is the adjective anxious (nervous, worried).
Persian
The correct spelling of the proper adjective is Scandinavian.
Persia
The likely term is the proper noun, an historical region, Persia (now Iran).
Those letters will spell the proper noun or proper adjective African.
The correct spelling of the proper noun or adjective is Jamaican.
The correct spelling of the proper noun or adjective is Portuguese.
That is the correct spelling of the proper adjective Virginian (from Virginia).
The proper adjective or term for people from China is Chinese.
An adjective describes a noun. You could potentially describe a person or thing as "Vietnamese".
The proper adjective for a person, thing, or characteristic is European (capitalized).
This could be the adjective serious, or series, or the proper noun Sirius.