$C_6H_5CH_3$ $\xrightarrow{CrO_2Cl_2} A$ $\xrightarrow{H_2O} B$
The functional group present in $B$ and the name of the reaction are:

For the reaction below, the structure of the product $Q$ is:

The major product of the following reaction is:
$CH_3CH_2CH=CH_2$ $\xrightarrow[Rh \ \text{catalyst}]{H_2/CO}$

Identify $P$ and $R$ in the given reaction sequence:
$Toluene$ $\xrightarrow[(2) H_3O^+]{(1) CrO_2Cl_2} P$ $\xrightarrow{R} Benzoic \ acid$

Identify $Z$ in the following sequence of reactions.
$C_2H_4Br_2$ $\xrightarrow[\text{(ii) } NaNH_2]{\text{(i) alc- } KOH} X$ $\xrightarrow[\text{Red hot}]{\text{Fe tube, } 873 \ K} Y$ $\xrightarrow[\Delta]{\left(CH_3CO\right)_2O / \text{Anhyd-} AlCl_3} Z$

Which of the following reaction sequences would be the best for the synthesis of $2$-pentanone?