No, a motion to dismiss is not a responsive pleading. Under the federal rules, the determination of "what's a pleading" is covered by Fed. Rule of Civil Procedure 7(a). If it isn't listed in Fed. R....
Pleadings are the formal allegations and responsives thereto, of parties in a lawsuit. Pleadings are usually filed to initiate a lawsuit (petition or complaint), and to file an official response,...
It is exactly that, what you plead initially.
Usually, people initially plead not guity to any offense. This is because pleading guilty admits guilt and will most definitely result in a conviction...