The increasing rate of $S_N1$ reaction in the following compounds is:

In solvolysis of $1,2$-dimethylpropyl $p$-toluenesulfonate in acetic acid at $75^\circ C$,(alkene + substitution products) will be formed by which mechanism?

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:

On monochlorination of $2-$methylbutane,the total number of chiral compounds is

In the following reaction $C_{6}H_{5}CH_{2}Br \xrightarrow[(ii)H_{3}O^{+}]{(i)Mg, \text{Ether}} X$
Product $X$ is

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 :