$$p$$-cresol reacts with chloroform in alkaline medium to give the compound A which adds hydrogen cyanide to form, the compound $$B.$$ The latter on acidic hydrolysis gives chiral carboxylic acid. The structure of the carboxylic acid is :

The oxidation state of chromium in the final product formed the reaction between $$K{\rm I}$$ and acidified potassium dichromate solution is :

On heating mixture of $$C{u_2}O$$ and $$C{u_2}S$$ will give :

Calomel $$\left( {H{g_2}C{l_2}} \right)$$ on reaction with ammonium hydroxide gives :