Sometimes / of

Hi,{Truth may sometimes come out of the devil's mouth. }There are two important problems to ask for your answering. I give my understanding with them, prior to your help. a. sometimes that shows the thing or the act on / through / by some occassions the question : Are the [on, through, by] the same realation as [to travel by car / to judge people by their apearience]? b. the [of ] in [of the devil's mouth]----used as [for] -----the devil's mouth is for / in favor of making [truth may sometimes come out]Thank you for your assistance.