Can i use kindly man when is an agenda to play a prayer?

No. Two reasons:

1) When Kindly Man is an agenda, it is no longer a character. The Prayer events require you to kneel a Holy character.

2) When Kindly Man is an agenda, it is not in play. You therefore cannot use it to pay the cost of a Prayer event any more than you can use a card in your discard or dead pile to pay the cost of a Prayer event.

~They should change his name to The Kindly Agenda at that point.