What is the product of the following reaction?
$Hex-3-ynal$ $\xrightarrow[(ii) PBr_3]{(i) NaBH_4}$ $\xrightarrow[(ii) CO_2 / H_3O^{+}]{(i) Mg / ether}$ ?

The oxidation of ethylbenzene with $KMnO_4$ yields which of the following compounds?

Consider the following reactions. From these reactions,which reaction will give carboxylic acid as a major product?
$(A)$ $R-C \equiv N \xrightarrow[(i) H^{+}/H_2O]{\text{mild condition}} R-CONH_2$
$(B)$ $R-MgX \xrightarrow[(ii) H_3O^{+}]{\text{(i) } CO_2} R-COOH$
$(C)$ $R-C \equiv N \xrightarrow[(ii) H_3O^{+}]{\text{(i) } SnCl_2/HCl} R-CHO$
$(D)$ $R-CH_2-OH \xrightarrow{PCC} R-CHO$
$(E)$ $\text{Benzoyl chloride} \xrightarrow[(ii) Br_2/H_2O]{\text{(i) } H_2/Pd-BaSO_4} \text{Benzoic acid}$
Choose the correct answer from the options given below:

The compound $X$ in the reaction is: $X$ $\xrightarrow{CH_3MgI} Y$ $\xrightarrow{\text{hydrolysis}} Mg(OH)I + CH_3COOH$

Identify compound $A$ in the following reaction.
$R-Mg-X + A$ $\xrightarrow{\text{dry ether}} R-COOMgX$ $\xrightarrow[\text{dil } HCl]{H_2O} R-COOH + Mg(X)OH$

What is the name of the reaction: $CH_3-CH=CH_2 \xrightarrow{CO + H_2O, H^+} CH_3-CH(COOH)-CH_3$?