1. "Reply" is a word we use to tell a story or for something more business-like. It sounds a bit distant. I wouldn't use it talking to a friend about his or her response to me. 2. This sentence sounds correct but it really depends on what the meaning behind this sentence is-the situation to which you are responding. 3. This is not how we use reciprocate. To reciprocate there is like a trade between people of some sort. What are the two of you trading. Your sentences are good grammatically, but I haven't heard sentences like this but still, very good work!

It looks like this is a situation where person A has feelings for person B but person B does not feel the same way about person A. In that case sentence 3 is most natural but somewhat ungrammatical and 'reciprocate' is a more formal or even clinical word. Sentences 1 and 2 are unnatural and seem as though the person can't respond to a message about feelings. A natural way to say 3 would be: I'm sorry but I don't feel the same way you do.

Thank you.

I think a more natural option would be... "I'm very sorry, but I don't feel the same way"

1 and 2 do not sound natural. #3 has a grammatical error (remove the word "for" and the sentence is correct). With this correction, the sentence sounds rather formal, but it is correct and natural.