What is the bond order in $N_{2}$ molecule?

During the change of $O_2$ to $O_2^-$ ion,the electron adds to which one of the following orbitals?

The correct set of symbols for the molecular orbitals given below is:

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. $\Psi_{MO} = \Psi_{A} - \Psi_{B}$	$I$. Dipole moment
$B$. $\mu = Q \times r$	$II$. Bonding molecular orbital
$C$. $\frac{N_{b} - N_{a}}{2}$	$III$. Anti-bonding molecular orbital
$D$. $\Psi_{MO} = \Psi_{A} + \Psi_{B}$	$IV$. Bond order

Consider the following statements.
$I$. In the conversion of $O_2$ to $O_2^{2+}$,bond order decreases.
$II$. In the conversion of $O_2$ to $O_2^{2+}$,magnetic property is not changed.
$III$. In the conversion of $O_2$ to $O_2^{2+}$,bond length decreases.
$IV$. $O_2^{2-}$ and $B_2$ have same bond order.
Identify the correct statements.

The formation of molecular orbitals can be described by the linear combination of atomic orbitals. Which one of the following correctly represents the formation of bonding molecular orbital from the atomic orbitals having wave functions $\psi_A$ and $\psi_B$?