A Thread for Questions on Movie Plots.

Ever watch a movie, and you know that you know the plots, characters, and other general info, but wanted to be sure, and confirm your theory, or just wanted another person's opinions?
Well, Lets ask here.

My starting Questions:

Even though I watched it a bunch of times, I had some confirmation questions about Rocky Horror Picture Show.

Why did Frank N Furter Kill Eddie? (Is it because he kept breaking the statues?)

Why did Rifraff Kill Frank N Furter? (Is it because Frank Killed Eddie?)

What was Frank's mission, that Rifraff had referred to near the end?

Why did Rifraff Kill Columbia? (Is it because She startled him?)

Why did Rifraff Kill Rocky? (Again, just to be cruel?)

Why did Rifraff Use the Candles on Rocky? (I think it was just to be cruel.)

I have my own theories, but wanted other people's opinions.