Harry Potter questions?!

Harry Potter questions?

I have a couple of questions about Harry Potter. I am not trying to play trivia. Just can's seem to tie a few things together.

1. What is the name of the insturment that they play in the beginning and in the end?

2. What is Professor Snapes role in all of this? I have not read the books. I have only seen the movies. From what I can tell he is always suspecting something is is up but coming to the wrong conclusion.

3. When Harry goes to the Shreeking Shack Black acts like he wants to kill Harry. He even says that he has waited 12 years for it. Then he directs it towards Peter why? I know that Peter is the one who tipped off Harry's parents.

4. What is up with the Malfoids? They they think that they are the heir to the house of Slitheran?

Thanks for the clarification.

1. i dunno
2. Snape started out to be a really mean teacher to Harry and all non-Slytherin students. But then again, Snape is really trusted by Dumbledore as Dumbledore claims that Snape has turned away from being a Death Eater, which he was before he joined Hogwarts. Snape, for me, is one of the most complex characters in the story coz until the sixth book, the reader is unsure whether he is on Voldemort's or Dumbledore's side... i have a feeling, though, that he is good now.
3. Black wasn't planning on killing Harry from the start. That's the twist in the story. Audience would think that Black was after Harry when he really is after Peter. The reason why it seems that he was after Harry was that Harry and Ron are best friends and Ron always (or almost always) had that pet rat with him.
4. Malfoys are arrogant and may sometimes be mistaken as the heir of slytherin because their family is pure-bloods. It means that for many generations, their family never accepted half-bloods or muggle breeds like hermione granger.

Hope that helps!