curtain raising vs opening night

curtain raising and opening night both are nouns.

Word	Noun	Adjective	Verb	Adverb
curtain raising	Yes	No	No	No
opening night	Yes	No	No	No

As nouns, curtain raising and opening night are synonyms defined as:

curtain raising and opening night: the first performance (as of a theatrical production)

Other synonyms of curtain raising include opening.

curtain raising (noun)	opening night (noun)
the first performance (as of a theatrical production)	the first performance (as of a theatrical production)