Loudest available ringtone

1) I would recommend the "Old Phone" tone. It is less likely to get masked by music or other ambient sounds than most other tones. And, if you're over a certain age, you're probably conditioned to it.

2) The phone will only ring as many times as the carrier allows. You can try calling your carrier and asking them to extend the time until the call goes to voice mail. However, at most you'll get two or three more rings. You cannot have the phone set to keep ringing until it gets answered.

The loudest ringtone would probably be 'Alarm'. I know it definitely gets my attention when sounded.