Both nitrogen and oxygen have electrons in the $2p$ orbital. In which of these is the electron-electron repulsion greater,and what is its effect?

The second ionization potential of elements is invariably higher than the first ionization potential because:

$B$ has a smaller first ionization enthalpy than $Be$. Consider the following statements:
$(I)$ It is easier to remove a $2p$ electron than a $2s$ electron.
$(II)$ The $2p$ electron of $B$ is more shielded from the nucleus by the inner core of electrons than the $2s$ electrons of $Be$.
$(III)$ The $2s$ electron has more penetration power than the $2p$ electron.
$(IV)$ The atomic radius of $B$ is more than $Be$.
(Atomic number: $B=5, Be=4$)
The correct statements are:

Which of the following is a favourable factor for cation formation?

Which of the following is not the correct increasing order of ionisation energy?

Why does the successive ionization enthalpy of an element increase in the order: $1^{st} < 2^{nd} < 3^{rd}$?