Must I make up the prayers I missed due to my ignorance and inability to hear and speak? And what are the recommended acts I can perform for my parents? And will the reward for fasting six days of Shawwal reach him if I dedicate it to him?

The deaf-mute is accountable for what he can understand through observation. Sheikh Ibn Uthaymeen was asked about the accountability of the deaf-mute, and he replied that he is accountable for what he comprehends of the religion through observation, and what he does not comprehend is waived for him. If he does not understand anything of the religion, and his parents are Muslims, then he is a Muslim by virtue of their lineage. If he is an adult and sane, his matter is with Allah, and he is outwardly judged as a Muslim as long as he lives among Muslims. There is a Hadith indicating that the deaf-mute will present his argument on the Day of Resurrection regarding what did not reach him of the religion, where Allah will send an angel messenger to them and command them to plunge into a fire. Whoever plunges into it will find it cool and peaceful, and whoever does not plunge into it will have the word of torment justified against him. As for performing prayers on behalf of the deceased, it is not legislated. What benefits the parent after his death is prayer for him, charity, Hajj, and Umrah on his behalf, and any righteous deed whose reward is dedicated to him.