Good news - yes you can generate a URL of a development store that can be used for SEO tests, speed tests, etc. Do get the URL, open the store and click on Online Store > Themes. Then click the ... button on the theme you want to test.
Then right click on the Preview link and select Copy link address. You can use this URL for your testing.
However, you should note that this URL is temporary and will stop working within an hour or so (from my experience).