Which one you will use depends on a lot of things. First, the facts:
Yes, but there might be small differences in the grades you get. However, a #2 filter will always give a softer result as a #3 filter, no matter on which paper you use it.
My humble opinion: the subtle differences of mixing up filters and papers are probably smaller than the differences introduced by the fact that you probably use another developer, enlarger and darkroom than the factory test facility. So you need to test anyway (I test by contact printing a step tablet).
Yes, you can. Again, get the datasheets of the paper - manufacturers of VC paper normally have color filtration values for the various grades. A starting point:
Yes, you can. Normal B&W paper, however, is not panchromatic - it only responds to a narrow band of wavelengths of light. Graded paper just responds to blue light, and variable contrast paper responds to blue and green light (but the amounts of blue and green light influence the gradation of the paper). Generally speaking, printing color negs on B&W paper won't give natural-looking results.
Kodak has a panchromatic paper, Panalure, available in 3 grades. If you want to get good results printing from color negatives, you should use this paper.
Of course, using normal B&W paper can give interesting effects, comparable with using orthochromatic film - experiment!