can I still be denied for answering that question unintentionally wrong?
Have you tried to have your answer corrected? You might want to do that, else it will look like you were intentionally lying.

Should I expect to be denied (as every one says that the first time you are always denied, no matter how clean and good you are.), or should I stop being so pessimistic about the situation.
Who is "everyone", and why do you think they know anything at all about your situation?

There is no policy of automatically denying a petitioner just because it's their first time.

We can't tell you whether or not you'll be denied. No one can. Your behavior and your work at getting yourself back on the straight and narrow will have to speak for you.