What will be $X$ in the following reaction?

$CH_3CONH_2 \xrightarrow{NaNO_2/HCl} X$

Find product $V$ in the following reaction sequence:
$CH_3-CH(CH_3)-COOH$ $\xrightarrow[H_3O^{+}]{LiAlH_4} I$ $\xrightarrow{PBr_3} II$ $\xrightarrow[ether]{Mg} III$ $\xrightarrow{CO_2} IV$ $\xrightarrow{H_3O^{+}} V$

$C_6H_5NH_2$ $\xrightarrow{NaNO_2/HCl} X$ $\xrightarrow{Cu_2(CN)_2} Y$ $\xrightarrow{H_2O/H^{+}} Z$
$Z$ is identified as :

Write a note on the preparation of carboxylic acid from alkyl benzene.

Acetic acid is manufactured by the fermentation of