Which of the following is used to convert olefins into aldehydes?

The reaction shown below is known as:-
$C_6H_5COCl + H_2 \xrightarrow{Pd-BaSO_4} C_6H_5CHO + HCl$
(Benzoyl chloride $\rightarrow$ Benzaldehyde)

$1$-Phenylethanol can be prepared by the reaction of benzaldehyde with the product obtained in the reaction between

The chemicals used for preparing acetophenone are:
$(A)$ $C_6H_6$
$(B)$ $CH_3COCH_3$
$(C)$ $CH_3COCl$
$(D)$ Anhydrous $AlCl_3$

$CH_3CH_2C \equiv N \xrightarrow{X} CH_3CH_2CHO$. The compound $X$ is:

In the following sequence of reactions,what is the end product $(D)$?
$C_2H_5Br$ $\xrightarrow{KCN} A$ $\xrightarrow{H_3O^{+}} B$ $\xrightarrow{LiAlH_4} C$ $\xrightarrow[573 \ K]{Cu} D$.