3
Using lightning.force.com/lightning in a URL link should be enough to have the user's page opened in Lightning Experience (LEX).
In terms of opening a specific app, I've queried the DurableId of the AppDefinition I'm interested in and a link format of:
yourDomainName.lightning.force.com/lightning/app/DurableId
That should then ensure it opens up in LEX with ...
2
Look at the Dashboard metadata.
With VS Code and the CLI installed, you can run the following command in the terminal to retrieve all dashboards
sfdx force:source:retrieve -m Dashboard
Otherwise, you could use the following package.xml and workbench to retrieve the dashboard by developer name.
<?xml version="1.0" encoding="UTF-8"?>
&...
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