Believing in certain things having particular effects is not considered polytheism, like believe in the evil eye or in magic. However, claiming that a particular stone has a certain effect requires proof.
It is obligatory on the father of the girl or her paternal grandfather to guard her welfare in accepting the marriage or refusing it. If the guardian in this case sees that the best interest of his daughter is not to marry this person, then he is permitted to refuse.
Learning music without practicing it is permissible, but such a thing is merely a theoretical assumption since learning music is associated with listening to it and playing it. It is prohibited to learn or play music that causes rapture.
It appears from some of the narrations that there are three inevitable signs. They are: the rising of the sun from the west, and the cry from the sky that will declare the reappearance of the Imam, and the swallowing of the earth in the desert. Other signs are possible. There is no doubt that Almighty Allah will establish undoubted clear evidence when he reappears, so it is better to delay paying attention to these issues to their designated times and not rushing to conclusions in this Godly matter, since He will clarify it at its appropriate time.