Which of the following is the reverse of photosynthesis?

Which of the following substances can undergo oxidation and release energy?

During a state of rest,the metabolic requirement is very low. This can be determined by:

$A$: In $PPP$ $(HMS)$,complete oxidation of one glucose molecule would produce $6CO_2$ molecules and $12$ $NADPH_2$ molecules.
$R$: It occurs in cytoplasm and chloroplast,in presence of $O_2$.

The term 'floating respiration' is used when the respiratory substrate is .........

How many $ATP$ molecules are produced via substrate-level phosphorylation during the complete oxidation of one glucose molecule in aerobic respiration?