As a word, Petra verses Petras did exist. The word Jesus called Peter means "little stones, or pebbles". Upon the "Big ROCK, Boulder" of the truth that Peter spoke concerning Christ, Jesus would build His church.
Now, as to what "most protestants" do or do not believe 1) What statistics prove this? and 2) What does it have to do with the price of tea in China? Most Protestants are like most Catholics these days and do NOT know Scripture. So, who cares what an uniformed decision says?
No it doesn't. "Petra" (feminine) is rock. "Petros" is a masculine form of the same word, which only exists as a proper noun. "Stone" would be "lithos", used by Peter is his epistle referring to the other believers (1 Peter 2:5).
Army or Marines?
I've got a preference. :>)
Lithos is the word for little stone or pebble