$C_6H_{13}Br + OH^{-} \to C_6H_{13}OH + Br^{-}$ is an example of

$2-$Bromobutane on heating with alcoholic $KOH$ forms

What is the product of the following $S_N2$ reaction?

What is retention and inversion of configuration? Explain with suitable examples.

Rate of $S_N2$ reactions depends on :

Arrange the following compounds in decreasing order of their reactivity for hydrolysis reaction:
$(I)$ $C_6H_5-CH_2-Br$
$(II)$ $C_6H_5-CH(Br)-C_2H_5$
$(III)$ $CH_3-CH_2-Br$
$(IV)$ $C_6H_5-CH(Br)-C_6H_5$