$$ \text { Which formula and its name combination is incorrect? } $$

$$ \text { In the complex ion }\left[\mathrm{Fe}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]^{3-} \text {, the co-ordination number of } \mathrm{Fe} \text { is } $$

On treating 100 mL of 0.1 M aqueous solution of the complex $\mathrm{CrCl}_3 \cdot 6 \mathrm{H}_2 \mathrm{O}$ with excess of $\mathrm{AgNO}_3, 2.86 \mathrm{~g}$ of AgCl was obtained. The complex is

The complex compounds $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{SO}_4\right] \mathrm{Br}$ and $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Br}\right] \mathrm{SO}_4$ are