Which of the following regarding halides nucleophilicity and their leaving group ability is(are) true?

The major product of the following reaction is :

The major product in the following reaction is :

Here, $\mathrm{Z}$ is:

The major product of the following reaction is:

The major products of the following reaction are :

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:

In the following reaction sequence, structures of $\mathrm{A}$ and $\mathrm{B}$ are, respectively

KI in acetone, undergoes S_N2 reaction with each of P, Q, R and S. The rates of the reaction vary as