Arrange the following compounds in decreasing order of the rate of electrophilic addition reaction:
$(P)$ $p$-vinylbenzaldehyde
$(Q)$ $p$-vinylanisole
$(R)$ $p$-methylstyrene
$(S)$ $p$-dimethylaminostyrene

Which of the following compounds is most reactive in $S_N 1$ reaction?

Given below are two statements :
Statement $I$ : $S_N2$ reactions are 'stereospecific',indicating that they result in the formation of only one stereo-isomer as the product.
Statement $II$ : $S_N1$ reactions generally result in the formation of product as racemic mixtures.
In the light of the above statements,choose the correct answer from the options given below :

What are $X$ and $Y$ in the following reaction sequence?

Chloroform on reduction with zinc dust and water gives:

Which of the following pairs is/are correctly matched?

Reaction	Product
$I$. $RX + AgCN$	$RNC$
$II$. $RX + KCN$	$RCN$
$III$. $RX + KNO_2$	$RONO$
$IV$. $RX + AgNO_2$	$RNO_2$