Which product is formed when a solution of $K_4[Fe(CN)_6]$ is added to a solution of $FeCl_3$?

Match List-$I$ with List-$II$:

$A$. Haber process	$I$. Fe catalyst
$B$. Wacker oxidation	$II$. $PdCl_2$
$C$. Wilkinson catalyst	$III$. $[(PPh_3)_3RhCl]$
$D$. Ziegler catalyst	$IV$. $TiCl_4$ with $Al(CH_3)_3$

Choose the correct answer from the options given below:

Aqueous solution of a metallic nitrate $X$ reacts with $NH_4OH$ to form $Y$,which dissolves in excess $NH_4OH$. The resulting complex is reduced by acetaldehyde to deposit the metal. $X$ and $Y$,respectively,are

$A$ solution of $FeCl_3$ when treated with $K_4[Fe(CN)_6]$ gives a Prussian blue precipitate due to the formation of:

Iron salt used in blue prints is:

Which ligand is used in the estimation of the hardness of water?