a. C6H12O6 = C6(H2O)6

b.

c. Yes, expected. Glucose is one isomer of fructose, and there are many kinds of glucose as well. Hence the different kinds of isomers will give different properties hence, different sweetness levels as well.

All nutrients are made up of chemical structures, hence it is impossible that “all organic chemical-free” diet really exists. A simple example is water, water itself is a chemical compound with a chemical structure (there is no such thing as water with no chemical structure).