Each of these three arguments has a conclusion different from the others. Thus, at most, only one of the arguments can actually be sound. But since designating any one of them as sound would be arbitrary, we must conclude that none of them is sound. That is, there are no contingent propositions. Every proposition is either necessarily true or necessarily false.
Contingency is simply an artifact of ignorance.
The fallacy arises in the ambiguity of the first premise. If x knows that p, then p must be true' If x knows that P, then P must be true. But if P must be true, then P cannot be false. Any proposition which cannot be false, is not only true, but necessarily true. Thus if x knows that P, then P is necessarily true.