Hi,
>>"Is that mean that when I create new text, dimension, or multileader style, I had better not copy it from predefined styles as Standard or Annotative? "
No, that's not a problem.
Use your own Layers, Styles, aso.. thats all.
>>"Also, could you please advise where I should get Layer 0 to avoid Thawing or Freezing it if I use the Visibility function from time to time for all layers together to Freeze them before Thawing just one I need to work with?"
1. These "Rules" are not holy, but they are good to bypass many possible problems.
2.If you know that freezing Layer0 makes trouble,
what you do now,
the next time you see unnormal things in Acad you will take a look there.
Knowing is the key, these rules are for not to have thinking about all details every second.
>>"I tried to find out on Forums but the solution offered was to go to App and download something."
No setting available to do this, so program extension are a good solution.
>>"but I treat that method as an improper one. "
All what helps you, is proper.
>>"I would prefer using standard tools and commands. "
You can set up a button to thaw and unlock Layer0
or to freeze-all-except-layer0.
But it should enought ti know about the issue.