Taubah and Repentance

Q: If we had committed any sin in the past and we are not sure if it was a sin, should we ask any Mufti or Aalim regarding that thing or just repent from all sins and move on in life believing Allah has forgiven us?

Q: Please can you tell me how do I make sincere repentance for the sins major/minor that I have committed in my life.

Q:

1. Is saying Astaghfirullah throughout one’s life fardh?

2. If a person repented without saying Astaghfirullah what is the consequence?

Q: Is it permissible for a person to reveal his past sins in the following situations:

1. With the intention of others taking lesson from it?

2. In the case where the sin is such that the one being spoken to is not involved in that sin, nor capable of doing that sin, and one reveals one's sin to him, to show him how one had changed one's life?

Q: How do I forget my past sins? They haunt me everyday.

Q: If a person recites this dua thrice أَسْتَغْفِرُ اللهَ الَّذِي لاَ اِلٰهَ اِلّٰا هُوَ الْحَيُّ الْقَيُّومُ وَأَتُوبُ إِلَيْهِ , Allah Ta'ala forgives all his sins. Does this forgiveness include major sins or is it only for minor sins?

Q: If someone says "Astaghfirullah alladhi la ilaaha illa huwal hayyul qayyum wa atubu ilayhi" 3 times, Allah will forgive all his sins. Does that include major sins?

Q: A person committed some mistake but alhmdullilah, Allah saved him from getting into a big mess. He thanked Allah but he gets thoughts that if he had avoided the mistake, things would have been different, etc. and dwells on his past. He always did some mistakes because of laziness or ignorance but Allah saved him. So, how should he thank Allah but not think of the mistake?

Q: I used to produce music and instrumentals but alhamdulillah I have repented from both listening to and making music. I am worried about the songs I released before, should I worry about them and try to get them deleted or am I free from it since I repented?

I also produced the background music for a podcast/show. I have sincerely repented from making any more music or sending/promoting my music. I feel absolutely horrible and I hope that this spread of my music doesn't come for me in my grave.

Q: I would like to ask the following question on repentance

1. Does repentance wipe out previous sins?

2. Am I always obliged to confess to the one whom I've wronged even if this might bring severe enmity?

3. How do I feel regret during repenting?