Do these answers work even when we change the values?
The value of any $st$-flow is at most the value of any $st$-cut, and they are equal if and only if the flow value is maximized and the cut value is minimized. Thus, statement (A) is false since $f$ isn't necessarily a maximum flow (since you claim (A) is true, maybe you forgot to mention that $f$ is a maximum flow, or you meant to say that the value of the cut is at least 50?).
Statement (B) is true, since if there is a flow and cut of equal value, then the flow is a maximum flow and the residual graph has no path from $s$ to $t$.

Of course, the actual values don't matter. Only the relationship between the flow value and cut value is relevant.