Yes. You should capitalize all religions, as they are proper nouns.
Yes it should always be capitalized.
I would say, un-Christian.
Yes, the Sacrament of Holy Communion should be capitalized as it is a proper noun referring to a specific religious ritual in Christianity.
Yes, you should capitalize the C in Century.
You should capitalize it if it is a brand name.
No, you should not. You should only capitalize a word when it is at the start of a sentence or when it is a proper noun.
Yes, you should capitalize "The Rotunda" as it is a specific place or location.
You should capitalize Colosseum when referring to the specific ancient Roman amphitheater in Rome.
It should not be capitalized.
No
no
No
Yes, it is correct to capitalize "Should" if it is used in a title as it is a noun in this context.
You should capitalize "Musical Theatre" when referencing the specific genre or art form.