All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is not permissible for a Muslim to supplicate against himself, whether it is an immediate or postponed supplication. Jaabir narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: “Do not supplicate against yourselves, your children, your servants, or your property, lest your supplication coincides with the time when Allaah The Almighty is about to confer upon you what you demand and thus your prayer may be readily answered.” [Abu Daawood]
It is obligatory for the Muslim to give up sins and if he swears to give it up, then the obligation will be more confirmed. If he breaks his oath, then expiation for breaking the oath is obligatory upon him and its characteristics are explained in Fatwa 82135. It is not necessary that your supplication will be answered, especially after repentance from the stated sin. Indeed, the Mercy of Allaah The Almighty is comprehensive and encompassing.
You should know that whoever turns to Allaah The Almighty with repentance, He The Exalted will accept his repentance. So, you have to repent to Him from all sins. As for the idea that Allaah hates you or not, then this is something related to the unseen that we do not know. There is nothing wrong in having such fear unless it makes one feel despair of the Mercy of Allaah The Almighty. Rather, it should encourage one to do good deeds and avoid evil ones. For more benefit, please refer to Fatwa 86527 regarding the conditions of repentance, and to Fataawa 83931 and 85275 regarding how the Muslim can be righteous and get closer to Allaah The Almighty.
On the other hand, mixing with bad friends most often has bad results. Whoever wants to mix with that kind of people should do that with insight or rather avoid them. Insight means that one should not mix with them while they are committing sins. Allaah The Almighty Says (what means): {And when you see those who engage in [offensive] discourse concerning Our verses, then turn away from them until they enter into another conversion. And if Satan should cause you to forget, then do not remain after the reminder with the wrongdoing people.} [Quran 6:68] Also, insight means commanding what is right and forbidding what is evil; for the one who stays silent (when people are committing evil acts) is a ‘mute devil’.
Similarly, listening to musical instruments is something prohibited as we have explained in the Fatwa 81545 and so is backbiting as explained in Fataawa 81748 and 82148. What is more serious and prohibited is not observing prayer at their due times. Anyway, studying is not an acceptable excuse that can allow this for you. If there is a conflict between studying and observing prayer, then observing prayer takes precedence. For more benefit, please refer to Fataawa 83812 and 88690.
Finally, we advise you to adhere firmly to repentance, as we have already stated, if you wish to win Paradise and be saved from Hellfire.
Allaah Knows best.