Step 11 is a bit different in latest Navigator. You’re only presented with the list of versions to install if you right/secondary click on the checkbox. If you just click the box it will default to the latest version, but the secondary click will allow you to get to the menu you see in the tutorial.
On Step 15, Just to clarify, are the “open with …” options greyed out, or is that menu not appearing at all? If the other options are just greyed out, make sure that you have JupyterLab or Jupyter Notebook installed in the environment. It looks like the tutorial assumes you already have those installed already. You can easily install those from the Environments tab (just like installing pandas), or from the Home tab.