Is the mark that appears on a man's forehead due to frequent prostration what is meant by the Almighty's saying: "Their distinguishing feature is on their faces from the trace of prostration"? And why does it appear on men but not women? And why do some men who prostrate frequently not have it appear on them?

The mark mentioned in Surah (definition) Al-Fath (سِيمَاهُمْ فِي وُجُوهِهِمْ مِنْ أَثَرِ السُّجُودِ - their mark is on their faces from the trace of prostration) is not the physical mark on the face from prostration. Rather, it is the good demeanor, humility, reverence, and modesty that appear on the face of a sincere worshiper. As for the physical mark, its appearance varies depending on the person's body type, how they prostrate, and what they prostrate on. This is not what is intended in the verse, nor is it considered proof of a person's righteousness.