The major product obtained in the following reaction is $:$

Match the reactions in List-$I$ with the features of their products in List-$II$ and choose the correct option.
| List-$I$ | List-$II$ |
| :--- | :--- |
| $(P)$ $(-)-1$-Bromo-$2$-ethylpentane $\xrightarrow{aq. NaOH, S_N2}$ | $(1)$ Inversion of configuration |
| $(Q)$ $(-)-2$-Bromopentane $\xrightarrow{aq. NaOH, S_N2}$ | $(2)$ Retention of configuration |
| $(R)$ $(-)-3$-Bromo-$3$-methylhexane $\xrightarrow{aq. NaOH, S_N1}$ | $(3)$ Mixture of enantiomers |
| $(S)$ $(3S, 5S)-5$-bromo-$3$-methylheptane $\xrightarrow{aq. NaOH, S_N1}$ | $(4)$ Mixture of structural isomers |
| | $(5)$ Mixture of diastereomers |

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

Which of the following undergoes nucleophilic substitution reaction according to the $S_{N}1$ mechanism?

Which of the following phrases are not correctly associated with $S_N1$ reaction?
$(1)$ Rearrangement is possible
$(2)$ Rate is affected by polarity of solvent
$(3)$ The strength of the nucleophile is important in determining rate
$(4)$ The reactivity series is tertiary $>$ secondary $>$ primary
$(5)$ Proceeds with complete inversion of configuration

Identify the major product formed in the following reaction: $3-$Bromo$-2-$methylpentane $\xrightarrow{Alc. KOH, \Delta}$ Major product