$A$ metal complex absorbed orange light. The colour in which it appears is

Blood haemoglobin contains the metal

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

Assign $A, B, C, D$ from the given type of reaction.
$NiCl_2 + 2dmg \xrightarrow{NH_4OH} Ni(dmg)_2 \downarrow$

The $INCORRECT$ statement is:

$PCl_5$ reacts with finely divided silver on heating and a white silver salt is obtained,which dissolves on adding excess aqueous $NH_3$ solution. Write the reactions involved to explain what happens.