Which of the following species is not paramagnetic?

Given below are two statements:
Statement $I$: $A$ $\pi$ bonding $MO$ has lower electron density above and below the inter-nuclear axis.
Statement $II$: The $\pi^*$ antibonding $MO$ has a node between the nuclei.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following statements is incorrect when $C_2$ changes to $C_2^{2-}$?

Correct decreasing order of bond order of oxygen species in $I$ to $IV$:
$(I)$ $Na_2O_2$
$(II)$ $O_2[AsF_6]$
$(III)$ $CsO_2$
$(IV)$ $O_2$

In which of the following ionization processes,the bond order has increased and the magnetic behaviour has changed?

The changes in bond length with respect to $N-N$ and $O-O$,when $N_2$ becomes $N_2^{+}$ and $O_2$ becomes $O_2^{+}$ are respectively