The strongest acid among the following is

The most acidic carboxylic acid is

The silver salt of a fatty acid on refluxing with an alkyl halide gives an

The strongest of the four acids listed below is

$A$ compound $(A)$ has the molecular formula $C_2H_4O_2$ and it gives the following reactions:
$(i)$ Addition of the above compound to a sodium carbonate solution gives effervescence of $CO_2$ gas and forms compound $(P)$.
$(ii)$ When compound $(P)$ is heated with sodalime,it gives gas $(Q)$. Identify $(A)$,$(P)$,and $(Q)$ and provide the reactions.

Predict the product of hydrolysis of the above molecule.