Sun systems-fulform of SUN?

of course not. But the sun is somewhat special in the fact that it is a lone star, most stars exist as part of binary or tertiary systems and other multi star clusters.

Yes, that's the idea of a "solar system". A star (sun) in the center, and planets going around it.

Yes, it is, or we would not be alive.

Well, you see, the answer to this question all depends on who you are talking about. My solar system only has one sun, yes but that does not necessarily mean that yours does. It is all a matter of...

The sun is at the centre of our solar system