The translation is "You are a pebble and on this boulder I'll build my Church". That boulder was "You are the Christ". It makes infinitely more sense that the Lord was talking about the "You are the Christ" and not one single apostle of 12 and then a continuing succession(sp) of apostles which is never once mentioned in the bible. This is why the whole Peter/pope thing is rejected by NonRC Christians.
No, the translation is "rock" in both cases.
"Petras" is rock, feminine noun.
"Petros" is masculine form corresponding to "Petras". Simon could not be called "Petras" because he is a man; no other gradation of meaning is in the text.
God giving a new name to someone is a sign of spiritual regeneration when an important historical role is given. It is used throughout the Bible, witness Abram - Abraham, Jacob - Israel.