The bond order and the magnetic characteristics of $CN^{-}$ are

Which of the following statements is correct for the peroxide ion $(O_2^{2-})$?
$A.$ It has completely filled $\pi^*$ antibonding molecular orbitals.
$B.$ It is diamagnetic.
$C.$ It has a bond order of one.
$D.$ It is isoelectronic with Neon.

What is the bond order of the $Be_{2}$ molecule?

Consider the given figure showing the formation of $H^{+}_2$ ion depending on internuclear distance versus potential energy of the system.
Which is the correct statement?

The pairs of species of oxygen and their magnetic behaviour are noted below. Which of the following presents the correct description?

Use molecular orbital theory to explain why the $Be_{2}$ molecule does not exist.