is pre-crisis earth one is actually alternative timeline? (Doomsday #7 spoilers)

[goldenknight2018]

after I read doomsday clock 7 I realize that it is possible dr manhattan travel to back to the past to the years 1940 on earth one,. (how to make spoilers)

but this is just theory.

everyone know JSA was fictional characters heroes comic books on earth one.

I read crisis on infinite earth series this story explains all that, just a year before booster gold and watchmen.

however, Earth one and earth two are not shared the same history, in other words, earth two is alternative history, not the timeline. for an example in classic Earth-Two stories, by the 1970s, Quebec is shown to be an independent nation autonomous from Canada.
South Africa abolished apartheid sooner than in the real world. Unlike other DCU depictions of Atlantis, the Atlantean countries of Poseidonis and Tritonis were ruled by a queen, not a king (along with its inhabitants displaying surface dweller features and no capacity for underwater survival, as the Atlantis continent had been raised) the Brooklyn Dodgers never move to the Los Angeles.

Barry Allen claims Gardner Fox's dreams were tuned into Earth-Two, explaining their depiction as a fictional world in earlier Barry Allen stories, maybe dr, Manhattan created the earth two.

so, if Attachment 71351the three dimwits, Attachment 71352johnny thunders, wildcat and dr fate Attachment 71353(dr, chaos) exist on earth one, then, whatever happens to
Atom (Al Pratt) of earth one
Doctor Fate (Kent Nelson) of earth one
Flash (Jay Garrick) of earth one
Green Lantern (Alan Scott) of earth one
Hourman (Rex Tyler) of earth one
Sandman (Wesley Dodds) of earth one
Terry Sloane(Mister Terrific) of earth one and
Dinah Drake(Dinah Drake) of earth one.
the question remains is, did they actually exist on earth one or perhaps never was exist at all?
or did dr manhattan change the earth one's past or someone else changes the past?
so I don't know whether pre-crisis earth one is actually alternative timeline or not?
so the mystery remains unsolved.

[theonetruebatman]

From what I understand from The Button Manhattan is somehow keeping all of the timelines held together but separate. I think they have either been splintered by his meddling or he is causing this himself. But yes. That would make it an Alternative.