Figma styles not applying

Hello all.
I have two files - File A and File B.
Currently, File A has no designs but has text styles in it. I duplicated File A as File B, so it also has the text styles as in File A.

Now I am designing in File A and applying the text styles also. Is there a way that I can copy the designs to File B, and the text styles are still applied?
I tried copy-pasting and cutting-pasting. It’s not working. None of the text styles is applied to the designs in File B.
I cannot use libraries because both files are in different teams. Also File B is supposed to be given to the client so I don’t want them to have access to my library

Please Help!!

Why don’t you want to duplicate File A now and move it to another team?

Because in File A, I keep adding new designs. It’s an ongoing project.
I don’t want to give access of File A to the client because of all the mess i make🙈

That’s why when I am done with a set of screens I paste it in File B. File B is also accessed by the developer. If the text and color styles are not applied its problematic for them and for me as well because I have to reapply the styles

Then I see 2 ways:

  1. Use style libraries (one in your team, one in another team) so that you can then use the “Swap library” feature.

  2. Apply styles manually or with plugins (as you are doing now).