Which is the best oxidizing agent to oxidize $CH_3CH=CHCHO$ to $CH_3CH=CHCOOH$?

Arrange the following in decreasing order of electrophilicity of carbonyl carbon.

The number of correct reaction$(s)$ among the following is $\qquad$

The major product of the following reaction is

In the presence of peroxide,styrene reacts with $HBr$ to give $X$. When $X$ is reacted with magnesium in dry ether followed by $CO_2$ and hydrolysis,it gives $Y$. Treatment of $Y$ with $PCl_5$ and then with $H_2, Pd-BaSO_4$ gives $Z$. What is $Z$?

An optically active alkyl bromide $C_4H_9Br$ reacts with ethanolic $KOH$ to form major compound $[A]$, which reacts with bromine to give compound $[B]$. Compound $[B]$ reacts with ethanolic $KOH$ and sodamide to give compound $[C]$. One molecule of water adds to compound $[C]$ on warming with mercuric sulphate and dilute sulphuric acid at $333 \text{ K}$ to form compound $[D]$. The functional group in compound $[D]$ will be confirmed by: