Compounds containing two $-OH$ groups on the same carbon atom are generally unstable,but which of the following is stable?

In which of the following reactions is the product $NOT$ correct?

Match the reactions in Column-$I$ with their products in Column-$II$.
| Column-$I$ (Reagents) | Column-$II$ (Product) |
| :--- | :--- |
| $(A) \ CH_3CHO + 2C_2H_5OH \xrightarrow{HCl_{(g)}} $ | $(i) \ (CH_3)_2C(OCH_2)_2$ |
| $(B) \ CH_3COCH_3 + CH_2OH-CH_2OH \xrightarrow{HCl_{(g)}} $ | $(ii) \ CH_3CH(OH)CN$ |
| $(C) \ CH_3CHO + HCN$ $\xrightarrow{OH^-}$ $\xrightarrow{H_3O^+}$ | $(iii) \ CH_3CH(OC_2H_5)_2$ |
| $(D) \ CH_3CHO + HCN \xrightarrow{OH^-} $ | $(iv) \ CH_3CH(OH)COOH$ |

What will be the major product?

The reagent with which both aldehyde and acetone react easily is

$CH_3-CO-CH_2-COOCH_3$ $\xrightarrow[H_2O]{H^{+}} A$ $\xrightarrow{\Delta} B$ $\xrightarrow{HCN} C$. What are $B$ and $C$?