Is the appearance of a faint, long black line on the forehead instead of the known circle a sign of prostration, despite infrequent commitment to prayer, and what are the deeds, obligations, and reprehensible acts related to the appearance of this sign?

The physical mark of prostration on the face is not what is meant by the "simah" (mark) mentioned in His (the Most High) saying: (Their mark is on their faces from the trace of prostration). This "simah" is the good demeanor, dignity, and humility that appears on the face of a sincere, devout worshipper. This mark is not considered proof of a person's righteousness. The questioner should prioritize maintaining prayer, as it is the pillar of religion, and he should repent sincerely for abandoning it and promptly make up for missed prayers, observing the correct order.