B. Add a home and garden page and redirect the home and garden category to this page.
C. Do something like multiste / multisore?
If you decide that this is not necessary, then write how to make the category tree in the sidebar do not show other main categories than one. For example, I enter the furniture and sidebar category, show me all the main categories should show only subcategories of one main category and show subcategories of the main category and all other parent categories (other departments)
Your request requires additional WooCommerce template files customization. You can try to create a multisite but note that you will have different websites, with different products and orders. So you will have to create absolutely separate websites. But it may be the best option in your situation.
I have a problem with one category (I put it in a private content) Shows me “No product categories exist.” Although I have set the template to show other categories if there is no sub category. It shows well everywhere and only in one shows such a message.