About the Domain Feature, Shopify recently added a new feature for Domains, so the old way to activate the Domain Feature won't work anymore, for certain stores.

However, I can now show you the steps to make this work, by following the new Shopify Markets process.

The first thing to do would be going to shopify > settings > markets: 

From there, you will have to click on add market on top:

In the following window you would have to pick the region you want to address this language to:

Then in the following screen, you would have to setup all the options about this Market, including the subdomain for the language:

After that, the Market will be active and the language should be correctly associated with it.

I hope this helps. Please, feel free to reach out back to us if you need any additional assistance.