Can a young man who has committed the abomination of sodomy and desires to repent and seek knowledge be granted success in acquiring righteous knowledge and forget what happened, or will that remain a stigma that pursues him?

It is good for a young man to abandon his beloved and repent to Allah. Allah forgives all sins; He extends His hand for the wrongdoer to repent, and He forgives sins no matter how great they are. Repentance erases what came before it. Those who repented succeeded in acquiring knowledge, engaging in da'wah (inviting to Islam), and performing good deeds. The Companions were polytheists before their conversion to Islam, then they became imams and luminaries. Fudayl ibn Iyad was a thief and repented, then he became the ascetic of the Two Holy Mosques.