In this case, yes. (But both singular and plural are used).

But keep in mind that's not always the case. It depends on whether the nouns are independent or not.

exp. Hamburger and fries is my favorite food - Το χάμπουργκερ με πατάτες τηγανητές είναι το αγαπημένο μου φαγητό, όχι φαγητά. They are not independent from each other, so you use singular instead of plural, both in English and in Greek. ^.^

No, the same way a "there are" is not needed here. ;)

Either translation is fine, practically, "church" translates to both "εκκλησία" and "ναός". "Temple", on the other hand, can only have the meaning of "ναός" ;)

The correct spelling is εκκλησία.

And it's feminine (like almost all words that end in -α but not -μα).

What was your entire answer?

Sorry, but it's actually correct. Και could be substituted with κι whenever the next word starts with a vowel. In this case, ένα does start with a vowel.

It's not mandatory, yet it's not incorrect. It's just a bit rare to see in common, informally written texts. ^.^

What do you mean?

What did you see that you think is not correct? What about it is not correct, in your opinion, and what would be the correct version?

Quite the opposite. Μουσουλμάνος refers to the person, and μουσουλμανικός is the adjective, that refers to everything else. :P I wouldn't say they are too hard to tell apart, since almost every word ending in -ικός is an adjective. ^.^

It had not been added, it's ok now.