Why one of NP-Complete problem had a polynomial solution then everyone of them has? Each NP problem is different, if one (even the hardest one) NP problem could be solved in polynomial time, I guess some related NP problems that could reduced to this one could also be solved in polynomial time. But why all? Does that mean all of other NP problems could be reduced to the one?
Some examples would be very helpful. 

Because If one "NP-complete" problem can be solved without providing a general solution to the entire class of NP-complete problems, then the problem wasn't an NP-complete problem to begin with - by definition.
