You need a stronger telescope than ordinary telescopes to see if one is a binary star. Like, you can't get these kind in shops… you have to make them, probably:-)
Its temperature, its mass, and its luminosity. Its size, nor distance have nothing to do with the colour of a star, bar maybe diffusion through additional materials when viewed from Earth.
Yes, there is a way to determine its structure just by observing the light emitted from it. Not only this but they can even determine if it is moving towards us or moving away. This is called the...