What is the ruling on one who masturbated during the daytime in Ramadan, then refrained from eating and drinking until Maghrib? Should he complete his fast or break it? And what is the ruling on delaying the making up of Ramadan days until the following Ramadan due to masturbation, and what should he do?

Masturbation is always forbidden, and it is even more forbidden in Ramadan. If it does not result in the emission of semen, then the fast is valid. If semen is emitted, the fast is broken and قضية (recompense/making up the day) becomes obligatory. If one did it out of ignorance that it invalidates the fast, some scholars do not obligate قضية upon him, but caution dictates it. If you know that masturbation is forbidden but are ignorant that it invalidates the fast, then you must make up the day. In the event that the fast is broken, one must refrain from all things that invalidate the fast for the remainder of the day. If someone delays making up Ramadan days due to a valid excuse, there is nothing upon him except making them up. If he delays them without a valid excuse, then in addition to making them up, he must pay a fidyah (expiation) of feeding one poor person for each day.