I do see type descriptions that mention INTJs feeling and actually being misunderstood. Usually we don't bother bemoaning that fact, however, whether in real life or online. We just make the effort to be understood when it is important, and otherwise move on.
No. Answering the MBTI questions from the perspective of what you think you should be will often yield an incorrect result. It is important to answer as you actually are, and that means what your preferences actually are, not your behavior. Many people take MBTI at work, and answer in their work personas, not based on their preferences when unconstrained by job demands, family expectations, etc. That is not your real type, just the type you pretend to be to get by in the world.
As for type changing, I have not seen a definitive answer on this, but everything I have read points to type being inherent, inborn. Our behavior will change as we grow and mature becasue we become more comfortable with our less-preferred functions and better able to integrate them into how we approach life, but that doesn't change our essential type.