Ethyl acetoacetate shows which type of isomerism?

The starting material is propene $(CH_3-CH=CH_2)$. The reaction with $H_3O^+$ (acid-catalyzed hydration) follows Markovnikov's rule to give $A$ (propan$-2-$ol,$CH_3-CH(OH)-CH_3$). The reaction with $(i) BH_3/THF$ followed by $(ii) H_2O_2/OH^-$ (hydroboration-oxidation) follows anti-Markovnikov's rule to give $B$ (propan$-1-$ol,$CH_3-CH_2-CH_2OH$). What is the relationship between products $A$ and $B$?

For the following four structures $I$ to $IV$,which statement is correct?
$(I)$ $C_2H_5-CH(CH_3)-C_3H_7$
$(II)$ $C_2H_5-CO-CH(CH_3)-C_2H_5$
$(III)$ $CH_3^+$ (Methyl carbocation)
$(IV)$ $C_2H_5-CH(CH_3)-C_2H_5$

In the reaction,as shown in the image,the number of possible isomers for the organic compound $X$ is

Functional isomerism is exhibited by the following pair of compounds:

Which of the following compounds does not exhibit tautomerism?