The following figure shows an amphibolic pathway. What are $P$,$Q$,and $R$?

$\beta$-oxidation occurs in .........

Given below are two statements:
Statement $I$ - $A$ stepwise release of chemical bond energy facilitates the utilization of a relatively higher proportion of that energy in $ATP$ synthesis.
Statement $II$ - Due to stepwise oxidation of respiratory substrate,the same pathway may be used for synthesis of another biomolecule.
In light of above statements,select the correct answer from the options given below.

Given below are two statements:
Statement $I$ - Reactions involved in Krebs cycle are anabolic and catabolic.
Statement $II$ - During oxidation of acetyl $CoA$,stepwise oxidation of the acetyl part of acetyl $CoA$ occurs.
In light of the above statements,choose the most appropriate answer from the options given below.

Choose the incorrect sentence$(s)$ regarding the amphibolic pathway.
$(1)$ Carbohydrates are generally used as substrates for respiration.
$(2)$ Fatty acids can first be degraded into acetyl $CoA$,which enters the respiratory pathway.
$(3)$ In the case of proteins,they are first broken down into amino acids,which are later converted into pyruvic acid and enter the respiratory pathway.
$(4)$ The respiratory pathway is involved in both anabolism and catabolism.
$(5)$ Glycerol would enter the pathway after being converted to $PGAL$.

Which of the following is a $2C$ intermediate compound formed in the respiratory breakdown reaction of fats and carbohydrates?