At $pH = 12$,what change occurs in $Cr_2O_7^{2-}$?

Which statement is incorrect?

$(a)$ Transition metals can act as catalysts because they can change their oxidation state. How does $Fe(III)$ catalyze the reaction between iodide and persulphate ions?
$(b)$ Mention any three processes where transition metals act as catalysts.

The correct statement about $Cr^{2+}$ and $Mn^{3+}$ among the following is (Given,atomic numbers of $Cr=24$ and $Mn=25$)

What is the correct order of basic character for the following transition metal monoxides?

Assertion $(A):$ $VF_5$ is stable while $VCl_5$ is not.
Reason $(R):$ Fluorine stabilizes the higher oxidation state due to its higher bond enthalpy.
The correct option among the following is