The man in the rear who can see both of his friends' hats but not his own says, "I don't know". The middle man who can see the hat of the man in front, but not his own says, "I don't know". The front man who cannot see ANYBODY'S hat says "I know!" How did he know the color of his hat and what color was it?

Answer :

The colour was Black and the Front Man got the answer by carefully listening to the others

Explanation: The front man knows that the man in the Rear who can see the other two hats did not see white hats, if he had seen White hat, he would have said that his own hat was white and the front Man also knows that the second man did not see White hat because if he had seen a white hat, he would have said his own hat was black since the man in the Rear said that he did not know. So the Front man knows that his hat was black by listening to the Rear and the middle man's Answers.

because he was a christian?

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.