Which is the most reactive halide towards $S_{N^1}$ reaction?

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:

The major product of the following reaction is:

In the above reaction,the maximum Saytzeff product will be obtained when $X$ is:

When $tert$-butyl bromide is heated with silver fluoride,the major product obtained is:

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