My organization creates another Partner for Development environment. Each dev has their own dev app. 

Agree. But you should add content_for_header contains "previewBarInjector.init();"to check theme preview as well.

It seems like your robots.txt is correct I tested the robots.txt before to hide my product details pages. It might take time for Search Engines like Google to re-index your site. If you want to speed up, you can try Google Search Console.

You can navigate to your Shopify Market Settings, and then click the market you want to add products to. If there is no market you want, then create it. And then you will see this section, click it and start modifying the products   

Maybe Shopify just golive new version. There is still SendBeacon failed error now while accessing Shopify Admin.

Totally agree. Our organization is doing this.