Describe the reaction of haloalkanes with $\mathrm{KSH}$.

The increasing order of reactivity of the following compounds towards reaction with alkyl halides directly is:

$\left(i\right)$

$\left(ii\right)$

$\left(iii\right)$

$\left(iv\right)$

The major product of the following reaction is:

The major product of the following reaction is:

The major product of the following reaction is:

In the reaction given below what will be the major product at the end :