The first ionization energy is the lowest for which of the following elements?

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 of $O$ is lower than that of $N$ and $F$.
Reason $R$: The loss of an electron from $O$ leads to a stable half-filled $p$ orbital.
In light of the above statements, choose the most appropriate answer from the options given below:

Which of the following is the $CORRECT$ decreasing order of ionisation enthalpy for the given elements?

In which of the following electronic configurations will there be a large difference between the second and third ionization energy?

What do the processes $(i) X_{(g)} \to X^+_{(g)} + e^-$ and $(ii) X^+_{(g)} \to X^{2+}_{(g)} + e^-$ represent?

How many ionisation energies can carbon have?