What is the function of glucose?

The normal amount of glucose in $100 \ mL$ of blood ($8-12 \ hours$ after a meal) is ........ $mg$.

What are $\beta - D - \text{glucose}$ and $\beta - D - \text{galactose}$ known as in relation to each other?

Which reagent among the following is used to confirm the presence of an aldehydic carbonyl group in glucose?

Which of the following is not possible in glucose?

On prolonged heating with $HI$,glucose gives a compound '$C$',which can be obtained by Wurtz reaction using sodium metal and compound '$D$'. Identify '$D$'.