The sources mentioned are generally safe, but be sure to check user reviews and ratings to ensure quality.
In general, MP3 files are compatible with a range of modern phones. Check compatibility with your phone's format before downloading.
Yes, many modern phones allow customization of ringtones for different contacts. Consult your phone's manual to find out how.
In your phone's ringtone settings, look for the option to reset ringtones to default settings.
Select the famous classic ringtone you downloaded from the options available in sonnerie mp3 settings.