What product is formed by mixing the solution of $K_4[Fe(CN)_6]$ with the solution of $FeCl_3$?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$(a)$ Chlorophyll	$(i)$ Ruthenium
$(b)$ Vitamin-$B_{12}$	$(ii)$ Platinum
$(c)$ Anticancer drug	$(iii)$ Cobalt
$(d)$ Grubbs catalyst	$(iv)$ Magnesium

Choose the most appropriate answer from the options given below:

State the importance of coordination compounds in photography.

Write the application of coordination compounds in black and white photography.

The metal present in $Vitamin \ B_{12}$ is

Identify the complexes formed in the following processes:
$I$. Mond's process for purification of nickel
$II$. Removal of unreacted $AgBr$ from photographic plates
$III$. Removal of lead poisoning from the body