Which is the major product expected from the following $S_{N}2$ reaction?

Compound $A$ with molecular formula $C_4H_9Br$ is treated with aqueous $KOH$ solution. The rate of this reaction depends upon the concentration of compound $A$ only. When another optically active isomer $B$ of this compound was treated with aqueous $KOH$ solution,the rate of reaction was found to be dependent on the concentration of both the compound and $KOH$.
$(i)$ Write down the structural formula of both compounds $A$ and $B$.
$(ii)$ Out of these two compounds,which one will be converted to the product with inverted configuration?

Heterolytic bond dissociation energy of alkyl halides follows the sequence:

Which halide will be most reactive towards $SN^2$ reaction?

Iodoform on heating with $KOH$ gives

An organic compound $A$ $(C_4H_9Cl)$ on reaction with $Na$ in diethyl ether gives a hydrocarbon,which on monochlorination gives only one chloro derivative. $A$ is: