2.How can I save Sweet Home 3D with its plugins to another computer as I am currently using it. Thank you if you can help

You don't. Install Sweet Home 3D on another computer and install one plugin: Plugin manager . As the name says it is a manager for plugins. It makes it very easy to install other plugins and it alerts you if there is a new version of a plugin. Use the Plugin Manager to install other plugins and keep them up-to-date.