How can one ascertain whether perfumes whose ingredients are not listed contain alcohol, and what should be done regarding perfumes with unknown ingredients, especially those like Sandaliya, Fleurdamour, Suwardparis, One Man Only, Al-Saroukh, and oil-based perfumes?

The alcohol content in perfumes can be determined by reading the ingredients listed on the packaging, or by discerning the scent. If the ingredients are not mentioned, or if there is no indication of alcohol presence, then there is no harm in using the perfume, because the default ruling for things is permissibility.