It seems that 2 correct choices are needed for each story completion, and also to unlock the best DREAM END.
Getting only 1 correct choice does unlock some back story, but not the pretty costume and the 完.
I ended up completing no story at all on the first TRUE END, and unlocked no scroll. Repeating the last choice to the DREAM END starts to get the first not-the-best dream scroll (i.e. BAD? END).
Following the guide, on the first run all choices would be answered correctly, and 夢 would end up in BAD END. However, answering some choices incorrectly, and 現 would end up in the same BAD END.
It depends on whether you want to see the bad end first.
There are two versions of good ends, however.
I think the publisher had her live longer, but not sure when was she ill. Maybe like 10? Still then, at what age did she marry (engage?) the first time? I think she got disowned to have her survive.
Also it is mentioned that he looks old on the train. The boy already looked teenage or more at the sick visit.
In the good dream end, I don’t think the deceased age is mentioned.
She not asking of her name saves the boy’s life in any case.
Momotaro got unlocked in Extra, and can be read about the happy end.
Maybe they fixed the story after that, in reality.