"Eure Zeitung ist gut."
A constant problem throughout these tutorials comes from the fact that English doesn't distinguish between formal and informal "you". This causes a lot of problems as one is trying to learn a language like German which does. Wherever ambiguity can cause a problem, the lessons should at all times specify which version is expected as an answer.
Both versions are correct and should be accepted.
No, I think "deine Zeitung" is "your newspaper (only you)" and "Eure Zeitung" is "your newspaper" (you, and someone else or even a third one) - plural.
I think "Ihre Zeitung" is formal, and "deine Zeitung" is informal.