Which of the following reagents is used to distinguish between acetone and acetophenone?

Arrange these compounds in decreasing order of reactivity for the nucleophilic addition reaction :
$I.$ Acid chloride $II.$ Aldehyde
$III.$ Ketone $IV.$ Ester
Select the correct answer from the codes given below :

Upon treatment with $Al(OEt)_3$ followed by usual reactions (work up),$CH_3CHO$ will produce

Cyclopentanone $\xrightarrow[\text{traces of } KOH]{HCN} A$ $\xrightarrow{LiAlH_4} B$ $\xrightarrow{NaNO_2, HCl} C$
$C$ is

The total number of $sp^2$ hybridised carbon atoms in the major product $P$ (a non-heterocyclic compound) of the following reaction is. . . . . . .

The order of reactivity of phenyl magnesium bromide $(PhMgBr)$ with the following compounds is: