You can copy all files that are in a WordPress project. E.g. via FTP. This cannot be prevented.
If you want to protect your Pro against something like this, use a licence model that regularly checks the permissibility of the installation against an external service. Then you can copy it but not use it without deliberately manipulating the theme files. You can find more information about this on the net.
WordPress doesn’t automatically update the theme when you make changes in the editor. You will need to go to the editor and export your theme to update the physical files so that wordpress will update all the files and the theme.json file. If you added your own css files you will need to add them again in the functions.php file or where every you added them. It probably a good ideal to export your theme once you made all the changes you want to keep so they are written into the theme files.