Glycerol heated with oxalic acid at $110^\circ C$ to form

Give the method of preparation of carboxylic acid from the reaction of a Grignard reagent with $CO_2$ with suitable examples.

What will be the final product of the following reaction sequence?
$CH \equiv CH$ $\xrightarrow{CH_3MgBr}$ $\xrightarrow{CO_2/H_3O^+}$ $\xrightarrow{HgSO_4/H_2SO_4}$ $\xrightarrow{Ag_2O, \Delta} ?$

In the reaction sequence $CH_3-C \equiv CH$ $\xrightarrow{CH_3MgBr, \text{Dry ether}} CH_4 + (A)$ $\xrightarrow[(i) \ CO_2]{(ii) \ H_2O/H^+} (B)$,$(B)$ will be

The reaction $CH_3-CH=CH_2 \xrightarrow[H^{+}]{CO + H_2O} CH_3-CH(COOH)-CH_3$ is known as:

Identify the compound $(B)$ in the given reaction.
$CH_3Cl$ $\xrightarrow{KCN} (A)$ $\xrightarrow{H^+ / H_2O} (B)$