Hanukkah can be used as an adjective or a noun.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for the proper noun 'Celt' is Celtic.Please note that a proper noun and a proper adjective is always capitalized.
Ghanian is the proper adjective for Ghana.
Since spice isn't a proper noun, it can't have a proper adjective. The adjective of spice is spicy.
Since writer is not a proper noun, it doesn't have a proper adjective.
"... and Happy Hanukkah!"
Yes.See also:More about Hanukkah
Hanukkah is a proper noun.
The proper adjective for Portuguese is "Portuguese."
The proper adjective for Haiti is Haitian.
The proper adjective for southwest is "southwestern."
Vietnamese is the proper adjective for Vietnam.
The proper adjective for George is Georgian.
The proper adjective for Siam is Siamese.
Freudian is the proper adjective for Freud.
The proper adjective for Georgia is Georgian.
The proper adjective for Mayan is "Mayan."