Thanks for reaching out.
Everything should work with Mandarin as long as the strings are translatable. I'll answer it according to the list
1) Yes, it should work and I recommend using WPML plugin for translation
2) This isn't theme or plugin related, but the capability of the translation plugin that you'll be using. Again, I recommend WPML plugin for translation. It works well with the cornerstone builder.
3) WPML plugin has menu syncing capability, you could use that. OR, simply create multiple menus and assign them to each header/footer of its language equivalent
4) WPBakery plugin and translatable and works well with WPML. But I'm not sure about the addons, they aren't bundled to the theme.
5) It depends on what you're displaying. If you're displaying the list/items of posts then it should automatically reflect to the translations you made to each post. But if you're creating a custom grid, then you can simply duplicate that grid and use each to their corresponding language. Example, use
grid 1 to
hello world English post, and
grid 2 to
hello world Mandarin post.
Let us know if you have further questions about the translation
And please check this as well https://theme.co/apex/forum/t/setup-translation/61