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

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

If the sum of bond orders of $O_2^{-}$ and $O_2^{2-}$ is $x$,then bond order of $O_2^{2+}$ will be (in $x$)

The electronic configuration of the $N_2$ molecule in its ground state can be written as: $KK[\sigma 2s^2 \sigma^* 2s^2 \pi 2p_x^2 \pi 2p_y^2 \sigma 2p_z^2]$. What is the bond order of the $N_2$ molecule?

Which of the following $M.O.$ has two nodal planes?

Assuming $2s-2p$ mixing is $NOT$ operative,the paramagnetic species among the following is: