How can one atone for past sins such as sodomy, listening to music, and sending forbidden links? And is expiation required for previous vows made out of ignorance?

Sincere repentance atones for past sins, no matter how great they were. Therefore, the repentant person must be truthful in their repentance, gain understanding in religious matters, and avoid the causes of falling into prohibitions. Remembering sins after repentance is good if it aids in perfecting the repentance. As for vows (nadhr), they must be fulfilled if they entail an act of obedience. Whoever doubts their vow is presumed to be free of obligation. Whoever is unable to fulfill their vow must offer an expiation for an oath (kaffarat yamin). If the vow was made to prevent oneself or to encourage oneself, one has the choice between fulfilling it or offering an expiation for an oath upon breaking it.