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

Consider the following changes $I$ and $II$ as shown in the figure. The correct statements about these changes $(I)$ and $(II)$ in accordance with $MO$ theory are:
$A$) In $(I)$ bond order increases by $0.5$ from the existing value.
$B$) In $(II)$ bond order decreases by $0.5$ from the existing value.
$C$) In both $(I)$ and $(II)$ magnetic property is changed.
$D$) In both $(I)$ and $(II)$ magnetic property is not changed.

Which of the following statements is not correct?
$I$) Bond length order: $H_2^- = H_2^+ > H_2$
$II$) $O_2^+, NO, N_2^-$ have the same bond order of $2.5$
$III$) Bond order can assume any value including zero up to four
$IV$) $NO_3^-$ and $BO_3^{3-}$ have the same bond order for the $X-O$ bond (where $X$ is the central atom)

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.

Which of the following sets of species have similar bond order?

Among the following,the species with identical bond order are