What is the ruling on fulfilling a husband's request for sexual intercourse during a voluntary fast or a fast to make up for missed days? And is it permissible not to make up missed prayers and suffice with supererogatory prayers?

A woman should not observe a voluntary fast while her husband is present except with his permission. He has the right to break her fast through intercourse if she observes a voluntary fast without his permission. As for an obligatory fast (Ramadan or a supererogatory fast with a constricted time), it does not require the husband's permission, and he does not have the right to make her break it.

As for an obligatory fast with an expansive time (like making up for missed days of Ramadan), the preponderant opinion is that it does not require the husband's permission, and he does not have the right to compel his wife to delay it.

If a woman fasts with her husband's permission, he does not have the right to invalidate her fast, even if it is supererogatory.

As for making up for missed prayers, they must be made up according to one's ability, in a way that does not harm the body or livelihood.