a) C6(H2O)6
CnH2nOn = Cn(H2O)n

b) drawing is on paper
c) Different isomers of fructose have the same chemical formula but different structures. Due to their different structures, we expect different isomers of fructose to have different physical properties such as sweetness.

It is impossible that have a chemical free diet.
For instance, food contains pesticides. Water is non organic, but it is found in most food we consume. Fish contains mercury and livestocks are injected with chemicals.