What is Schiff's reagent?

In the following conversion,
$C_6H_5CN$ $\xrightarrow[(ii) H_3O^+]{(i) MeMgBr} X$ $\xrightarrow[H_3O^+]{NaOH/I_2} Y$
the major products $X$ and $Y$,respectively are

Which of the following compounds would undergo aldol condensation?

Write a test to differentiate between pentan$-2-$one and pentan$-3-$one.

The products formed in the following reaction,$A$ and $B$ are

$A$ tertiary alcohol $H$ upon acid-catalysed dehydration gives a product $I$. Ozonolysis of $I$ leads to compounds $J$ and $K$. Compound $J$ upon reaction with $KOH$ gives benzyl alcohol and a compound $L$,whereas $K$ on reaction with $KOH$ gives only $M$.
$1.$ Compound $H$ is formed by the reaction of
$2.$ The structure of compound $I$ is
$3.$ The structures of compounds $J, K$ and $L$,respectively,are
$(A)$ $PhCOCH_3, PhCH_2 COCH_3$ and $PhCH_2 COO^{-} K^{+}$
$(B)$ $PhCHO, PhCH_2 CHO$ and $PhCOO^{-} K^{+}$
$(C)$ $PhCOCH_3, PhCH_2 CHO$ and $CH_3 COO^{-} K^{+}$
$(D)$ $PhCHO, PhCOCH_3$ and $PhCOO^{-} K^{+}$
Give the answer for questions $1, 2$ and $3.$