Acetone and acetaldehyde are differentiated by

What are $X$ and $Y$ respectively in the following reactions?
$C_6H_5COOH \xrightarrow{X} C_6H_5CHO$
$C_6H_5CHO \xrightarrow[OH^-, 293 \ K]{C_6H_5COOH} Y \text{ (Major product)}$

Identify the organic compounds $P$, $Q$, and $R$ in the following reaction sequence: $C_3H_6 \xrightarrow[ii) H_2O_2/NaOH]{i) BH_3} P \xrightarrow[anhydrous medium]{CrO_3} Q \xrightarrow[ii) H_3O^+]{i) CH_3MgBr} R + Mg(OH)Br$.

Identify the test from the following in which an aldehyde,when boiled with an ammoniacal silver nitrate solution,deposits silver.

Which of the following cannot give a yellow $ppt.$ with $I_2/NaOH$?

Number of products in the given reaction:
$C_6H_5CHO + CH_3CHO \xrightarrow{OH^-} \text{Product}$
will be