What is the correct order of electron affinity for the elements of the oxygen group in the periodic table?

$A = 1s^2\, 2s^2\, 2p^4$,$B = 1s^2\, 2s^2\, 2p^5$,$C = 1s^2\, 2s^2\, 2p^6$. $A, B$ and $C$ are atoms/anions of the same element. Which one is correct? (One of $A/B/C$ is a neutral atom)

Which will have the maximum value of electron affinity among $O^x, O^y$ and $O^z$ ($x, y$ and $z$ are $0, -1$ and $-2$ respectively)?

Within each pair of elements of $F$ and $Cl$,$S$ and $Se$,and $Li$ and $Na$,respectively,the elements that release more energy upon an electron gain are

Which of the following represents an exothermic reaction?

Which of the following pairs of elements would have a more negative electron gain enthalpy?
$(i)$ $O$ or $F$
$(ii)$ $F$ or $Cl$