Which of the following compounds will react with ethanolic $KCN$?

The correct order of reactivity of $PhMgBr$ with:
$(I)$ $Ph-CO-Ph$
$(II)$ $CH_3-CHO$
$(III)$ $CH_3-CO-CH_3$
is:

$C_{7}H_{10}O$ reacts with $CH_{3}MgBr$ to give a compound $C_{8}H_{12}O$ which gives a positive iodoform test. Identify the structure of $A$.

In the given reaction sequence,the conversion of $X$ to $Y$ is an example of:

Which of the following compounds shows tautomerism?

Identify the product for the following reaction: $CH_3-CO-CH_3 + HO-CH_2-CH_2-OH \xrightarrow{HCl} ?$