What is the ruling on rebinding the Mushaf if some pages are missing or torn? And what is the ruling on burning it if it is more severely torn or old and no longer needed? And what is the method for burning it?

There is no harm in binding the Mus'haf, whether completely or partially. If the Mus'haf becomes damaged and unusable, it is permissible to dispose of it by burning or burying it in a respectful place to preserve its sanctity, as the Companions, may Allah be pleased with them, did. Ibn Battal opines that burning books containing the name of Allah is permissible, as it is an act of honoring them and protecting them from being trodden upon.