Which one is correct?

I was practising grammar and came across a few exercises that confuse me:
The new sports centre ______(open) next month but I doubt if it ________(complete) by then!
I wrote: “opens” and “will have been completed”. The second one is correct, according to the key. But the first one isn’t, the key says “is due to open”. Why is that wrong?

We’d better hurry up, I think they _______(close). I wrote “are closing” and the correct answer is “are going to close”. Why is that wrong?

The play doesn’t start until 8.30 so I think we _______(have) time to eat something first. I wrote “have” but the correct answer is “will have”. I still think “have” might be correct if we’re for example standing infront of the theatre and thinking what to do until the play starts.

The Prince _______(give) a speech to local community leaders this evening.
I wrote “is going to” which is correct but the key says “is giving” is correct as well. Can present simple continuous be used anytime when “going to future” is used?
I also have a question about articles: The Prince is correct as I can see in the exercise a few lines up but what about The Prince _______(any name)? Is there an article needed or not?

Thank you for your answers. :slight_smile:

But the first one isn’t, the key says “is due to open”. Why is that wrong?– ‘Opens’ is perfectly fine.

I wrote “are closing” and the correct answer is “are going to close”. Why is that wrong?-- Nothing is wrong at all with your answer.

I wrote “have” but the correct answer is “will have”.-- And ‘have’ is perfectly fine too, wherever you are standing.

Can present simple continuous be used anytime when “going to future” is used?-- Not any time, but usually. Present continuous refers to near future.

The Prince is correct as I can see in the exercise a few lines up but what about The Prince _______(any name)? Is there an article needed or not?-- No article: Prince Charles, Prince Ranier, Princess Leia