Does the reprehensible become forbidden and the permissible obligatory if the parents command one to abstain from it or do it, and when is a son's action considered disobedience to his parents?

Obeying parents is obligatory with certain conditions: there must be a benefit for them in the matter, and no harm should befall the child by performing it. If what they commanded is permissible, has a benefit for them, and causes you no harm, then obedience is obligatory; otherwise, it is not. Obedience to them in disliked (makruh) and doubtful matters is obligatory if the aforementioned condition is met. If your parents do not see you doing a permissible or recommended act that they forbade, there is no harm in doing it, because no harm will result to them from that.