"Open" is an adjective. "Opened" is not. Therefore, "We are open" is correct, but "we are opened" is not correct. "Opened" is, however, a verb.

What is correct is open or is opened?

Open does not refer to any past event, while opened does. Both refer to the same current state, but opened opens the door to an earlier narrative, if you will. The door was once closed*, and someone or something changed it. The use of opened indicates a larger history for the object that open entirely ignores.

Has opened in a sentence?

Sentence examples for it has opened from inspiring English sources. It has opened its first international office outside of its SF headquarters, in Tokyo, Japan. It has opened its doors to several Western embassies. It has opened its curator's apartment, an architectural gem designed by Franco Albini, to the public.