$A$ pair of isoelectronic species having bond order of $1$ is

The wave functions of $1s$-orbitals of two hydrogen atoms are $\psi_A$ and $\psi_B$. $\psi_A$ and $\psi_B$ are linearly combined to form two molecular orbitals ($\sigma$ and $\sigma^*$). Which of the following statements are correct?
$I$. $\sigma^*$ is equal to $(\psi_A - \psi_B)$.
$II$. In $\sigma$-orbital,one nodal plane is present in between two nuclei.
$III$. The energy of $\sigma$-orbital is lower than the energy of $\sigma^*$-orbital.

Identify the correct increasing order of energies of molecular orbitals for the $F_2$ molecule.

$H_{2}$ molecule is more stable than $Li_{2}$ molecule,because

From elementary molecular orbital theory,the electronic configuration of the singly positive nitrogen molecular ion $N_2^+$ is:

$CN^-$ and $N_2$ are isoelectronic,but $N_2$ is chemically inert compared to $CN^-$. The reason is: