Which is the best method to prepare cycloalkene from cyclohexanol?

$C_6H_6$ $\xrightarrow[(ii)\,\,Zn-Hg/HCl]{(i)\,\,CH_3COCl/AlCl_3}$ $(P)$ $\xrightarrow[(ii)\,\,H_2O/K_2CO_3]{(i)\,\,NBS}$ $(Q)$
Major product $(Q)$ of the following sequence is:

The product formed when glycerol reacts with $PCl_5$ is -

In the esterification reaction of $p$-toluic acid with methanol $(CH_3^{18}OH)$,the product $A$ is:

What is the compound $D$ in the following reaction sequence?
$CH_3CH_2OH$ $\xrightarrow{P + I_2} A$ $\xrightarrow{Mg} B$ $\xrightarrow{HCHO} C$ $\xrightarrow{H_2O} D$

Alcohols react with Grignard reagent to form