Which of the following configurations represents atoms of the elements having the highest second ionization energy?

Given below are two statements. One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The first ionization enthalpy for oxygen is lower than that of nitrogen.
Reason $R$: The four electrons in $2p$ orbitals of oxygen experience more electron-electron repulsion.
In the light of the above statements,choose the correct answer from the options given below.

The correct order of $C$, $N$, $O$ and $F$ in terms of second ionisation potential is

The correct order of second $I.E.$ of $C$,$N$,$O$,and $F$ is:

Which of the following electronic configurations has the highest ionization enthalpy?

Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.