What is the correct order of bond lengths in the following molecules? $I. O_2, II. O_2^+, III. O_2^-, IV. O_2^{2-}$

The number of species from the following which are paramagnetic and with bond order equal to $1$ is:
$H_2, He_2^{+}, O_2^{+}, N_2^{2-}, O_2^{2-}, F_2, Ne_2^{+}, B_2$

Give the electron configuration,bond order,magnetic property,and energy diagram for the beryllium $(Be_{2})$ molecule and discuss its existence.

When the reaction $O_2 + e^- \to O_2^-$ occurs,identify the molecular orbital into which the electron is added.

In which change do both the bond order and the number of unpaired electrons increase?

Given below are two statements:
Statement $(I)$: The correct sequence of bond lengths in the following species is:
$O_2^+ < O_2 < O_2^- < O_2^{2-}$
Statement $(II)$: The correct sequence of number of unpaired electrons in the following species is:
$O_2 > O_2^+ > O_2^- > O_2^{2-}$