Answer:
1) The branched metabolic reaction pathway is attached.
2) The most prevalent reaction is L-->N
Explanation:
The reaction that eventually will prevail is the formation of the N molecule.
When Q and S are in high, they will inhibit the formation of P and R which are the molecules that form them. So, Eventually, there will not be P and R molecules, and hence, there will not be any more Q and S molecules.
L can still form equally M and N molecules. But as M forms O, and O inhibits M formation, with time, the higher O concentration is, the less M formation there will be.
On the other hand, N has no molecule that inhibits its production. So L turns to N formation, predominating this reaction.