Hey, well to answer you Firstly, I have to point out, when I saw this episode, I was about 10 years old, it was on a german channel and very late at night xD
1.)Ran was definetly in it too.
2.)The killer is unknown but the suspects are male(i think)
3.)The real weapon is unknown to me
4.)I think that there is only one female death, but I am not sure. I do know that there is only a "vampire" type death involved,
5.)I have no idea about the motive.
6,)The mansion is located in a private estate type of place, like, very out of the way, with a large courtyard involved. I think there is actually an evening party in it, but i am not sure.
7.)I think that the case is a two parter, but I am not sure about it, since I haven't saw the whole thing.
I hope this helps