Which of the following reagents reacts differently with $HCHO$,$CH_3CHO$,and $CH_3COCH_3$?

Benzaldehyde can be converted to benzyl alcohol in concentrated aqueous $NaOH$ solution using

In the following reaction:
$HC \equiv CH \xrightarrow[{Hg^{2+}}]{{H_2SO_4}} 'P'$
Product $'P'$ will not give:

Write the structures of the products of the following reactions:
$(i)$ $CH_3-CH=CH_2 \xrightarrow{H_2O/H^+}$
$(ii)$ (See image)
$(iii)$ $CH_3-CH_2-CH(CH_3)-CHO \xrightarrow{NaBH_4}$

Identify the product in the following reaction :
$3$-acetylbenzaldehyde $\xrightarrow{Zn-Hg, HCl}$ Product

The products formed in the following reaction,$A$ and $B$ are