Is it obligatory to make up prayers after repenting from masturbation due to ignorance of the ruling on ghusl (ritual bath) from it, and is ghusl for menstruation sufficient for ghusl for janabah (major ritual impurity)?

You are on a path of great good, and your question is not a public declaration of sin. You are not obligated to inform your mother, and your repentance is sound and accepted. You are not required to make up the prayers and fasts as long as you are not certain that semen, which necessitates ghusl (ritual bath), was discharged. Therefore, your prayers and fasts are valid. Leave off making up [the obligations] and increase in supererogatory acts and righteous deeds. Do not preoccupy yourself with this matter, and close the door of waswasah (whispers/obsessive thoughts) to yourself. Purity is not a condition for the validity of fasting; the fast of one who is in a state of janabah (major ritual impurity) is valid. And even if we assume the discharge of semen, you are not required to make up the prayers due to your ignorance, and this is a very strong opinion to close the door of waswasah.