I put an image without music to simplify:
I can’t put a double bar e at the end of the “intro” section. If I put one in, the rehearsal duplicate of part “A” disappears. Is it possible or is it against the rules of engraving?
How to make the repeat at point No.2 (last measure) replay from “A” and from the beginning? when doing “play” or especially when exporting the audio?
Well, I’d claim it is not, especially as the latest development version of Lilypond made a point of adding this capability. So that’s as to rules. As far as Dorico goes, I don’t know at this point. And people have differing views of what the rules of engraving are anyway. Dorico generally follows Gould, an author I particularly dislike when it comes to rules!
For my first question I found to do it under:
Engrave options->barlines : Barlines at end of system coiciding with start repeat
Yes, the ability to change which barline appears at the end of a system, when the following system starts with a start repeat barline, was added in Dorico 4. You can also do this for an individual instance by selecting it and using the Barline at end of system property, in addition to the project-wide default in Engraving Options (if you have Dorico Pro).
For controlling where repeats go back to, you might want to use repeat markers instead of “plain” repeat barlines (which in general go back to the nearest start repeat barline before them).
I finally use D.S and put “segno” , but is it possible that the repetition do A1 then A2 . It jump directly to A2 i.e the D.S ignore repetition of the A.
found under playback->repeats