The only thing I didn’t get was the old Cap thing. Everything else sort of made sense to me as I assumed the creation of alternate realities (Ancient One) / second timeline due to the actions of their time travel. The Cap thing essentially starts to unravel things, but before that everything works.
So, my understanding of it is... They created an alternate universe each time they changed something. Then, if they go back to the moment they changed something and put it back (the stones) they closed that alternate reality. This is what the movie says.
So Cap takes all the stones back. I'm assuming New York is fixed because Cap gets the scepter first and then the Tesseract debacle doesn't happen. 1/6 and Time Stone 2/6
Morag should be fairly straightforward. 3/6
Vormir is weird. They took the soul stone with a sacrifice. How does one put it back? Whatever. 4/6
Putting the Aether back into Jane? Also very strange but okay. 5/6
The tesseract in 1970. 6/6. BUT he obviously meets Peggy which should create a new reality because he changed something. So he shouldn't live out in the original universe but somehow he does. If collecting the stones is the only thing that creates a new reality, then there you go. He lives out in the original timeline and all realities are closed.
So Cap takes all the stones back. I'm assuming New York is fixed because Cap gets the scepter first and then the Tesseract debacle doesn't happen. 1/6 and Time Stone 2/6
Morag should be fairly straightforward. 3/6
Vormir is weird. They took the soul stone with a sacrifice. How does one put it back? Whatever. 4/6
Putting the Aether back into Jane? Also very strange but okay. 5/6
The tesseract in 1970. 6/6. BUT he obviously meets Peggy which should create a new reality because he changed something. So he shouldn't live out in the original universe but somehow he does. If collecting the stones is the only thing that creates a new reality, then there you go. He lives out in the original timeline and all realities are closed.