What religion are you?

To the extent that religion and race are parallel in usage, I'd choose #3, "Of what race/religion are you. Otherwise, I'd say, "What is your religion?"
Personally, I wouldn't be comfortable using any of the three. I might say, "Of what sect are you?"

(I'm glad your question is in the singular.)

I'd say, "What is your religion?"

Hi

sitifan1. What religion are you?
2. What religion are you of?

3. Of what religion are you?

Which of the above sentences is acceptable?

1. What religion are you? - I am ..........

3. Of what religion are you?

Even better would be, "If you don't mind my asking such a personal question, what is your religion?" Religion can be a sensitive topic.

Hi,

It certainly is a sensitive topic in English culture.

Who would you say this to? In what situtation?

I can't really imagine asking my colleagues or friends such a question. I certainly would be shocked if Khoff asked me.

sitifan1. What religion are you?
2. What religion are you of?

3. Of what religion are you?

Which of the above sentences is cacceptable?

While all three are understandable, What is your religion? is better, subject to all the caveats mentioned earlier in the thread.

CJ

what is the proper version?

His 2 parents are 2 different religions.
His 2 parents have 2 different religions

Is it more formal, more correct?

His parents are of different religions.