Payment method preference for APP - F110

Hi All Experts,

I have doubts regarding APP - F110.

1 ) While determining payment method for successful execution of APP what is the preference ranking ? Which level picked up first.

2 ) On additional log Tab how these 2 below option effects on payment method selection ? as well as please tell me significance :

A - Payment Method Selection in all cases

B - Payment Method Selection if not successful

If anybody has gone across and having idea for above, please share guidance.

Regards,

Sharvari Joshi.