Gheebat and Mocking

Q: If I made gheebat of a person and I repent to Allah. The person is not aware of me making gheebat of them, do I still need to ask them for maaf?

Q: Is it permissible to eavesdrop on a conversation if I am the one being spoken about?

Q: If someone insults the Prophet Muhammad (Sallallahu Alayhi Wasallam) then should there be any punishment for him, looking at the fact that he did not kill any innocent human being, and as Allah Ta'ala says that we should forgive anyone who says bad words to us, and we should reply with Salaam? I need references from Quran and the Saheeh Hadith, only then I will believe.

Q: If somebody uses "ma shaa Allaah" sarcastically in response to a sarcastic sentence, this is surely wrong, is it not? And is this kufr? Secondly, if someone laughs at the use of sarcasm here have they done kufr?

Q: If a person has committed backbiting against someone, and wants to make taubah from backbiting, and the person he was backbiting about does not know about it, does one have to go and tell the person I said this and that about you, make maaf, or can one beg forgiveness from Allah and do some good action and send the sawaab to the person?

Q: Is lying in a joke permissible?

Q: Is joking with friends and family allowed? If yes please explain to us to what extent and with what type of relatives can we joke?

Q: If you bad mouth or swear someone under your breath, meaning no one can hear you, is that still backbiting or sinful?

Q: I wanted to ask I often backbite about my father and so I understand I give away my good deeds. My question is if I ask forgiveness and he forgives me will I get my good deeds back or not?

Q: I have a question that I have a distant uncle who is sick and old and that when I  inquired about his health from my brother over the phone he said that he's not well and doesn't recognise people, today when I met with another relative he was asking me about this uncle and I said that he's not well and that he doesn't recognise people. My question is that is it a gheebat (backbite)?  Please advice me.