The typical reaction of an aldehyde is

Given below are two statements :
Statement $I :$ The nucleophilic addition of sodium hydrogen sulphite to an aldehyde or a ketone involves proton transfer to form a stable ion.
Statement $II :$ The nucleophilic addition of hydrogen cyanide to an aldehyde or a ketone yields amine as final product.
In the light of the above statements,choose the most appropriate answer from the options given below :

Which of the following has the most acidic hydrogen?

Predict the major product of the following reaction sequence:

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

$A \xrightarrow{} (CH_3)_2C=CH-CO-CH_3$. $A$ is: