Must one make up prayers and fasting, given that one does not recall masturbating during Ramadan, was previously ignorant of its prohibition, and does not recall the emission of anything necessitating ghusl?

We hope that you are not sinful for your ignorance of the prohibition. If you are not certain about the emission of semen, you are not required to make up the fast or the prayer. However, if you are certain of its emission during Ramadan, then whoever commits an act that breaks the fast, being ignorant of what excuses them, is not required to make up the fast. Nevertheless, it is more cautious to make up those days to avoid the disagreement of those who do not consider ignorance an excuse. As for prayer, the majority of scholars believe that it is obligatory to make up prayers for one who prayed without purification, and this is more cautious, even though Sheikh al-Islam holds that the ignorant person is not required to make up the prayer. If you are certain that it was semen and you did not perform ghusl, then you must make up the missed prayers. If you are unable to, then investigate and act according to what you predominantly believe to be true.