Explain the reaction of glucose which shows the absence of the free aldehyde group in pentaacetate of D-glucose.

Identify the product $\mathrm{Y}$ in following reaction $\mathrm{Maltose}\stackrel{ \mathrm{Hydrolysis} }{⟶}\mathrm{X}\underset{\left(\mathrm{excess}\right)}{\overset{\mathrm{dil}.{\mathrm{HNO}}_3}{\to }}\mathrm{Y}$

Number of stereo centers present in linear and cyclic structures of glucose are respectively:

In the above reactions, the enzyme $\mathrm{A}$ and enzyme B respectively are :-