Will Allah (the Most High) hold His servant accountable for the sins he committed, such as listening to music, cursing, mocking, and backbiting? And is there a way to erase, forgive, and atone for these sins, transgressions, and iniquities?

The servant will be held accountable for everything. Deliverance and the effacement of sins are easy for whomever Allah makes it easy for, for Allah's mercy encompasses all things. He accepts the repentance of His servant if it is sincere and assists him in it, forgiving his sins no matter how great they are, as Allah Almighty says: "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.'"