It’s really up to you. As a developer, I prefer working locally but if you do not develop but only add/remove/update themes and plugins, then a subdomain can be great. This way, you can freely break your website without disturbing anyone. Nowadays, lots of hosts providers are offering to create staging website in one click. … Read more
You can start by doing a full filesystem and database and put the same thing running on your staging environment under a different domain. Don’t do configuration under this installation or if you do bare in mind that changes will be lost since you want to periodically sync the production database with the staging one … Read more
how to move particular functionality to staging server
Copy the keys and salts from the production site? Try updating the password with WP-CLI?
Staging site offline
Administrative capabilities are the essential part of the WordPress core, and while you may be able to block access to wp-admin directory and through this to the administrative UI, there are other ways to administer a WordPress site, namely XML-RPC and at some point the JSON API. The easiest approach assuming all of your plugins … Read more
WordPress has an option to protect each page’s content using a password. That is done using the right panel just below/under the publish button. However if you want to hide the entire site and make it visible only to users who are logged-in, then you should consider using a “maintenance plugin” or a “construction plugin”, … Read more
Siteground should be able to tell you if your sites share a DB (or it should be evident from whatever control panel they provide). That said, it’s generally not advisable to mess with the DB of a live site. Make your changes and configure your plugins on stage, then when you’re happy, replicate that work … Read more
Staging only for Theme Files and Changes
I fear that there does not exist an answer that is going to make you happy. There is no (easy/good) solution for this problem. In most cases, the production (staging) environment does only touch the code (FTP-files) of a WordPress website, while the live version makes changes to the database (e.g. adding content to it). … Read more