Translation:Is this the Italian or the French flag?
And you're absolutely sure "Is this flag Italian or French?" is unacceptable?
Ta flaga. True, but it's close enough, I reported it and forgot to write here, I think it should be accepted now.
You are never penalized for not using Polish characters. It is just treated as typos. But I really recommend using it. If your keyboard is English, then you can just use Polish instead, it has everything you need for English in the same place, plus of course everything you need for Polish.
This and that should be interchangeable in this context.
Also, it is not necessary to say 'or the Italian flag', simply 'or Italian Flag' is fine.
Both 'this' and 'that' are accepted.
Lack of article before the second flag (French) is accepted.
Why can't you say: "This is the Italian or French flag?" - when this has EXACTLY the same meaning as: "Is this the Italian or French flag?" ?
It is the word order of an English question. That's why you can construct a sentence that way and put a question mark at the end of it - and it's still valid as a question.