Which of the following statements is incorrect?

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $Cu^{2+}$ in water is more stable than $Cu^{+}$.
Reason $(R):$ Enthalpy of hydration for $Cu^{2+}$ is much less than that of $Cu^{+}$.
In the light of the above statements,choose the correct answer from the options given below:

Number of unpaired electrons in $Mn^{2+}$ is

Which of the following elements has the maximum first ionisation potential?

Of the following outer electronic configurations of atoms,the highest oxidation state is achieved by which one of them?