What is the correct order of electron affinity for the given groups?

Which of the following ions is most unlikely to exist?

Consider the following conversions:
$(i) \, O_{(g)} + e^- \to O_{(g)}^{-}, \Delta H_1$
$(ii) \, F_{(g)} + e^- \to F_{(g)}^{-}, \Delta H_2$
$(iii) \, Cl_{(g)} + e^- \to Cl_{(g)}^{-}, \Delta H_3$
$(iv) \, O_{(g)}^{-} + e^- \to O_{(g)}^{2-}, \Delta H_4$
Based on the given information,which statement is incorrect?

The electron gain enthalpy (in $kJ/mol$) of fluorine,chlorine,bromine and iodine,respectively,are:

Explain the following :
$(1)$ $Pb^{4+}$ acts as an oxidizing agent but $Sn^{2+}$ acts as a reducing agent.
$(2)$ Electron gain enthalpy of chlorine is more negative as compared to fluorine.

For electron affinity of halogens,which of the following is correct?