What type of reaction is the following: $CH_3CH_2Cl + KOH(aq.) \rightarrow CH_3CH_2OH + KCl$?

Observe the following reactions:
$1$. $C_6H_5-CH=CH_2 + HBr \rightarrow X$
$2$. $C_6H_5-C(CH_3)=CH_2 + HBr \rightarrow Y$
$3$. $C_6H_5-CH=CH_2 + HBr \xrightarrow{(C_6H_5COO)_2} Z$
The correct order of reactivity of $X, Y, Z$ towards $S_N1$ reaction is:

Observe the following reactions. The order of reactivity of $x, y, z$ towards $S_{N}1$ reaction is:

Explain the stereochemistry of $S_{N}2$ reaction with a suitable example.

What is the product formed by the reaction of $C_6H_5CH = CHCH_3$ with $HBr$?

When alcoholic $KOH$ is reacted with $CH_3CH_2Cl$ to form an alkene,which species acts as the attacking reagent?