Does a person's prayer before puberty make up for missed prayers after puberty? If not, how does he make up for what he missed? Is he rewarded for his prayer before puberty? And is his parent rewarded for it?

If the missing prayers are due to sleep or unconsciousness, they must be made up, based on the Almighty's saying: "And establish prayer for My remembrance," and the Prophet's (peace be upon him) saying: "Whoever sleeps through a prayer or forgets it, let him pray it when he remembers it." If the negligence in prayer stems from laziness, some scholars consider the one who does so to be a disbeliever. If he repents, he is not obligated to make up the prayers, but he must renew his faith and increase his acts of obedience. However, making them up is more cautious. As for prayer before puberty, it does not count as making up what was missed after it. Prayers missed after puberty are an established debt, whereas what was done before puberty is supererogatory, while what was missed after it is an obligation. In the Hereafter, Allah may forgive His servant or complete what was deficient in his obligatory prayer through his voluntary acts. In the Hadith: "Indeed, the first thing a servant will be held accountable for on the Day of Resurrection from his deeds is his prayer. If it is sound, he will have succeeded and prospered. If it is corrupt, he will have failed and lost. If there is any deficiency in his obligatory prayer, the Lord, the Exalted and Glorious, will say: 'Look, does My servant have any voluntary acts with which what was deficient in the obligatory prayer can be completed?'" This may mean completing deficiencies in sunnahs and postures, or entirely missed obligatory prayers.