What must a young man do for his sins to be forgiven and his repentance accepted after committing sodomy, masturbation, and drinking alcohol, and feeling intense remorse for them?

Praise be to Allah for your repentance. The sins you committed are not disbelief that takes one out of the fold of Islam. Allah's mercy is vast, and there is no sin that Allah does not forgive if a servant repents with sincere and truthful repentance. Allah Almighty said: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" Sincere repentance makes the servant like one who has not sinned. Therefore, you must be sincere in your repentance, increase your supplications for forgiveness, have a good opinion of Allah, and increase your supererogatory acts of worship and good deeds, while expelling the whispers of Satan.