Arrange the following in the increasing order of the tendency of $\sigma$ donation.

$\mathrm{C}, \mathrm{N}, \mathrm{O}, \mathrm{F}\left(\mathrm{halogen}\right)$

Arrange the following in the increasing order of the strength of the ligands:

$\left(1\right) \mathrm{Br}, \left(2\right) {\mathrm{S}}^{2-}, \left(3\right) {\mathrm{NO}}_2^{-}, \left(4\right) \mathrm{CO}, \left(5\right) {\mathrm{H}}_2\mathrm{O}, \left(6\right) {\mathrm{CN}}^{-}, \left(7\right) {\mathrm{NH}}_3, \left(8\right) {\mathrm{NO}}_3^{-}$

Among the given options, which complex is diamagnetic?

(i) $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$,

(ii) $\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_2$,

(iii) $\left[\mathrm{Cr}\left({\mathrm{H}}_2{\mathrm{O}}_6\right)\right]{\mathrm{Cl}}_3$,

(iv) $\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{Cl}}_2$