What is the phenomenon of rapid interconversion of $\alpha-D-$glucose into $\beta-D-$glucose in solution called?

The given osazone can be obtained by:

Glucose on reaction with $Br_{2}$ water gives

Hydrolysis of sucrose is called

Write a note on the cyclic structure of glucose.

Given below are two statements:
Statement $I$: The two cyclic forms of $D-(+)-glucose$ ($\alpha$ and $\beta$ anomers differing at $C1$ hydroxyl orientation) are two anomers of $D-(+)-glucose$.
Statement $II$: The open chain forms of $D-glucose$ and $D-fructose$ contain three similar chiral carbons at $C3$, $C4$, and $C5$.
In the light of the above statements, choose the correct answer from the options given below: