Which of the following compounds gives a ketone with a Grignard reagent?

Which of the following reactions is best for the preparation of an aldehyde from a primary alcohol?

The reaction is given as follows:
$Ph-CO-N(CH_3)(OCH_3) + 2CH_3MgBr \xrightarrow{H_3O^+} (P)$
Product $(P)$ is:

In the reaction:
$C_6H_5-H \xrightarrow{[X] / AlCl_3} C_6H_5-C(=O)-CH_2-C_6H_5$
$[X]$ will be:

Consider the following statements. Acetophenone can be prepared by:
$1$. Oxidation of $1$-phenylethanol
$2$. Reaction of benzaldehyde with methyl magnesium bromide
$3$. Friedel-Crafts reaction of benzene with acetyl chloride
$4$. Distillation of calcium benzoate

The conversion,$PhCN \to PhCOCH_3$,can be achieved most conveniently by reaction with