Identify the major product formed from the following reaction sequence:
$CH_3-CH=CH_2$ $\xrightarrow[(i) HBr]{(ii) NaOH}$ ${\xrightarrow[(iii) Cu/573 \ K]{(iv) Ba(OH)_2, \Delta}} ?$

$4$-formylbenzoic acid on treatment with one equivalent of hydrazine followed by heating with alc. $KOH$ gives the major product:

The rate of hydrate formation for the given compounds is:

In the presence of dil. $HCl$,compound $A$ is converted to a constitutional isomer $(B)$. Compound $B$ is:

Ethyl ester $\xrightarrow{CH_3MgBr} P$. What will be the product $P$?

$A$ compound $(X)$ possesses a smell like bitter almond.
$(i)$ It does not give the Fehling test.
$(ii)$ It gives the silver mirror test.
$(iii)$ Compound $(X)$ gives orange precipitates of benzaldehyde $2,4-$dinitrophenylhydrazone with $2,4-DNP$.
Identify compound $(X)$ and provide its chemical reactions.