1. if kindly man is taken control by the opponent and killed, will he become opponent's agenda if he has no agenda? and if he has agenda, where will kindly man go?
my opinion: since it's a replacement effect ( replace being killed), it'll become its controller's agenda if he has no agenda and will go to its owner's dead pile if its controller has agenda.
2. can arya (the narrow sea version)'s ability be triggered when kindly man becomes an agenda?
my opinion: i think not, cause his being killed is replaced.
3. can river raid be triggered by dark star?
my opinion: i think not, cause dark star's ability is also a replacement effect, it is not discarded at all.