The best way to check compatibility is to check the information provided by the site or app where you download the ringtone. They will indicate the file types supported by different phone models.
The use of popular songs as ringtones may be subject to copyright and legal restrictions. It is recommended to use free and legal ringtones available on dedicated sites or applications.
The procedure for adding a custom ringtone to a specific contact varies depending on the phone and operating system you are using. Usually, you can go to the contact's settings and set a custom ringtone from there.