Name a transition element which does not exhibit variable oxidation states.

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

What is the highest possible oxidation state exhibited by manganese $(Mn)$?

In which of the following is variable valency observed?

Given below are two statements:
Statement $I :$ The $E^{\circ}$ value of $Ce^{4+} / Ce^{3+}$ is $+1.74 \, V$.
Statement $II :$ $Ce$ is more stable in $Ce^{4+}$ state than $Ce^{3+}$ state.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following is wrongly matched?