Is it permissible to apply musk to the hair and private parts to remove odors resulting from perspiration? And is it true that the Prophet, may Allah's prayers and peace be upon him, used to apply ambergris to his hair?

There is no objection to using musk and other types of perfumes on the hair, body, or clothes. This is a beloved Sunnah of the Messenger of Allah, peace and blessings be upon him, especially in gatherings. The virtue of perfuming oneself on Friday has been mentioned, and the Prophet, peace and blessings be upon him, used to perfume himself as Aisha, may Allah be pleased with her, mentioned. There is no evidence reported for placing ambergris on the head.