Is the young man considered to have committed the major sin of deceit and treachery if he was unaware of its forms?

Doubt concerning the commission of a sin is not taken into consideration, and the default is innocence thereof. One who commits a sin, being ignorant of its prohibition, is excused if someone like him would be ignorant of that. However, for that whose prohibition is well-known among Muslims, ignorance of it is no excuse. One must dismiss obsessive whispers and trust that Allah accepts the repentance of one who repents with sincere repentance, and that person becomes as if they had not sinned, as the Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin," and "Regret is repentance."