No. 1 is fine. In this sentence, complete
is an adjective and it's used to describe the current condition or state of the building.
No. 2 is fine. Is completed
is the passive voice in the simple present tense and is used here the same way the adjectiev is used in no. 1.
No. 3 is fine. In this sentence, has been completed
is the present perfect in the passive voice, and completed
is the past participle. The present perfect is used here to show that the completion of the building was very recently accomplished.