What is a keyword in SAQL? And what case must it be in?

Creating an Einstein Discovery story involves:

A CRM Analytics consultant at Cloud Kicks is trying to upload data using an External Data API and the CSV file with the data was uploaded successfully. Upon analyzing the data using a lens, they find they are unable to perform any mathematical operations as all the data and fields are treated as dimensions.
What is causing the problem?

A CRM Analytics consultant is working on Sales dashboards with multiple datasets and advanced queries in the Sales Analytics app.
Sales managers in the organization have been given Editor/Manager access to the app, whereas sales reps have been given Viewer access.
Some dashboards that are in progress are not ready to be rolled out to sales reps and should only be viewable by sales managers.
How should the consultant accomplish this?

Universal Containers has a Sales Manager dashboard- They have a compare table that displays the count of Customers and the Sum of Annual Revenue per year and per Account type. A consultant is asked to add more groupings to enhance details about their customers.
What is the maximum number of grouping columns that the consultant must be aware of in order to continue using a compare table versus creating the query using SAQL?