It is unlawful to listen to music which usually causes ‘tarab’. ‘Tarab’ means the psychological interaction with the music or singing, whether it leads to joy, sadness, pride or any other emotion.

It is prohibited to harm the neighbors, and it is highly recommended to be kind with the neighbors and to deal with them in a good way.

It is not permitted for one to be obscene and lewd in such a manner that he doesn't care what people say about him. If there is nobody present to hear it, then it is permissible.

It is obligatory for the son (or the daughter) to obey the parents if the disobedience leads to ‘uqooq’, i.e. it is considered an offense and aggression against them. It is also obligatory to obey them if the son (or the daughter) expect that his disobedience would cause harm to them. Otherwise, it is not obligatory to obey the parents, although it is better to do so anyway.

Although it is not obligatory to treat the grandparents in the manner one should treat the parents, and the strong ties that one has with his parents may not be with one’s grandparents too, there is no doubt that one should deal with the grandparents in a good manner.

You should pay back what you have taken from him, and it is not necessary for you tell him what you had done in the past. The monthly payments can be considered as repayments to him, if you are paying on his behalf, rather than contributing.

If the music causes ‘tarab’ then it is not permissible to listen to it. ‘Tarab’ means the psychological interaction with the music or singing, whether it leads to joy, sadness, pride or any other emotion.

Yes, it is permissible to conceal one’s age, as it is not considered to be lying. Lying is giving false information.
Lying about one's age is Prohibited.

It is not permissible.

It is prohibited to swear at a believer.

Based on compulsory precaution, one should not desert a believer for more than three days, even if the latter was wrongful to him. It is sufficient to satisfy this obligation by greeting him (e.g. saying 'salam alaykum'). If the other party insisted on the abandonment, he will become the deserter.
This prohibition has three exceptions:
First: if the desertion was to forbid the wrong.
Second: if the desertion would lead to a benefit that the Sharia recommends, like - for example - if desertion leads to paying attention towards a truth that could remain hidden without such desertion, or similar cases.
Third: if the reestablishing the relationship would lead to demeaning oneself. One should be careful in not confusing arrogance and anger with self-demeaning.

It is obligatory on every believer to enjoin the good and forbid the wrong if the conditions are met.

One should look for its owner and give it to him. With despair of finding the owner, one should give it as a charity on the owner’s behalf. If the papers have the name(s) of Allah written on them, one should dispose of them by placing them in a river or the like. You should not be afraid of its effect and depend on Almighty Allah, and recite Ayat-ul-Kursi as it is known that it is beneficial in such cases.

If the believer commits sins openly then it is allowed to backbite and criticize him.

Yes, it is permissible to backbite a person who is openly committing sins, and amongst the greatest of sins is oppression and aggression.

It is not permissible to play betting games even if it was without betting.

It is not allowed to play chess, cards or any similar games that are based on competing and invented to make money, even without betting.

It is not correct to commit a greater sin because of committing a lighter one, since committing suicide is greater than adultery. You should repent from what you have done as Almighty Allah forgives all sins.
You can guard yourself by getting satisfied through marriage whether it is permanent or temporary. May Allah help you pass this hardship.

Islam does not allow suicide in any situation.