Which of the following is used as a catalyst for preparing Grignard reagent?

Which of the following reaction$(s)$ can be used for the preparation of alkyl halides?
$I$. $CH_3CH_2OH + HCl \xrightarrow{Anh. ZnCl_2}$
$II$. $CH_3CH_2OH + HCl \rightarrow$
$III$. $(CH_3)_3COH + HCl \rightarrow$
$IV$. $(CH_3)_2CHOH + HCl \xrightarrow{Anh. ZnCl_2}$

$Cl_2$ reacts with $CS_2$ in the presence of an $I_2$ catalyst to form:

Explain the preparation of alkyl halides by halogen exchange methods.

The synthesis of alkyl fluorides is best accomplished by

$C_2H_5Cl + AgF \longrightarrow C_2H_5F + AgCl$
The above reaction is called: