$HBr$ reacts with $CH_2=CH-OCH_3$ under anhydrous conditions at room temperature to give:

The major product obtained in the following reaction is $C_2H_5ONa + (CH_3)_3C-Cl \rightarrow$

The reaction of $p-$bromobenzyl chloride with $NaCN$ in ethanol gives:

$A$ dihalogen derivative '$X$' of a hydrocarbon with three carbon atoms reacts with alcoholic $KOH$ to give another hydrocarbon which forms a red precipitate with ammoniacal $Cu_2Cl_2$. '$X$' gives an aldehyde upon reaction with aqueous $KOH$. What is the compound '$X$'?

The most reactive molecules towards $SN^1$ reaction are:

The following compound on hydrolysis in aqueous acetone will give: