Which among the following compounds is obtained when calcium formate is dry distilled alone?

In the following reaction sequence,identify the compound $Z$ if the starting material is toluene $(C_6H_5CH_3)$:
$C_6H_5CH_3 \xrightarrow{CrO_2Cl_2 / CS_2, H_3O^+} Z$

In the reaction $CH_3CN + CH_3MgI \to A \xrightarrow{H_2O/H^{+}} B$,the compound $B$ is

Which of the following reagents is used in Gatterman-Koch formylation of arene?

Which of the following reactions can be used to obtain a ketone $(R_1COR_2)$,where $R_1 = R_2$ are alkyl groups,in a single step?

Which of the following is Rosenmund reduction?