What is the bond order of $O_2^{2-}$?

According to Molecular Orbital Theory,which of the following statements is/are correct?
$(A)$ $C_2^{2-}$ is expected to be diamagnetic
$(B)$ $O_2^{2+}$ is expected to have a longer bond length than $O_2$
$(C)$ $N_2^{+}$ and $N_2^{-}$ have the same bond order
$(D)$ $He_2^{+}$ has the same energy as two isolated $He$ atoms

From the following,identify the ions with the same bond order.
$I$. $CN^{-}$
$II$. $N_2^{+}$
$III$. $O_2^{2-}$
$IV$. $NO^{+}$

Which molecule has the highest bond order?

In dinitrogen tetroxide $(N_2O_4)$,there:

The bond stability of $N_2$,$N_2^{-}$,and $N_2^{2-}$ varies as: