First of all, you may understand it as anaerobic, because at that time, after all, there was hardly much oxygen in the air.

As for the second point, I wonder if you have learned the Birth of Life (probably this lesson)? We know that there was no life on the early earth. There were only a few small molecules at that time; After a period of time, these small molecules become relatively large molecules; Then, these macromolecules form a kind of "macromolecular group", where these "macromolecular groups" have certain "metabolic" ability, and they will absorb useful substances from the external environment and discharge the waste substances in the "molecular group".

These "macromolecules" gradually developed and formed the early life forms of the earth: they had a "membrane" isolated from the external environment, thus creating an internal environment; They have their own core "molecular cluster"-> early genetic material, which makes the traits of their offspring relatively stable; And their "eating method" has always maintained the form of the early "macromolecular group" era, that is, they still directly use external substances instead of internal old substances, that is, heterotrophic forms!

Is there anything you don't understand?