What is the ruling on one who did not know of the obligation of ghusl after seminal emission for nine years? Should he make up the missed prayers, and should he also make up the votive prayers for masturbation along with them?

There is a difference of opinion regarding the necessity of making up prayers performed by a person without ghusl (ritual bath), due to ignorance of its obligation. As for the vow, it falls under the category of a vow of obstinacy (nadhir al-lajaj), and the one who made the vow has the choice between fulfilling it or offering an expiation for an oath (kaffarat yamin). If one wishes to follow the opinion of the majority of scholars, which obligates making up the missed prayers, then one should first make up the missed prayers. After that, one has the choice regarding the vow: either offer expiation or perform those prayers after making up the missed ones, because what is obligatory by religious law takes precedence over what is obligatory by a vow.