If the muadhdhin gives the adhan at the time when Fajr comes, then he must stop having intercourse as soon as he hears the adhan. If he does not do that, then he must make up the fast as well as offering the expiation.

1- If a man had intercourse with his wife while fasting and he was unaware of the ruling, and he thought that the kind of intercourse that is haram is the kind in which ejaculation occurs, then he does not have to do anything. 2- If he knew that intercourse is haram, but he did not know that there is expiation for that, then he has to offer the expiation.

If the nosebleed reaches the stomach without any deliberate action on the part of the fasting person, it does not break your fast.

There is nothing wrong with simply rinsing out the mouth while fasting so long as the water does not enter the throat of the fasting person.

There is no harm for a fasting person to taste food as needed. If they accidentally swallow it, there is no sin, and they can continue their fast.