On-premises data gateway: An on-premises data gateway is only required if the data source is located within a private, on-premises network (e.g., a local SQL Server). For cloud-based data sources like Azure SQL, SharePoint Online, or public web feeds (like OData), Power BI can connect and refresh the data directly over the internet without needing a gateway. Therefore, a gateway is not always needed.

Scheduled refresh: When you publish a dataset to the Power BI service using Import mode, the data is a static copy taken at the time of publishing. To ensure the reports and dashboards reflect the latest information from the source, you must configure a scheduled refresh. This tells the Power BI service to periodically reconnect to the data source and update the dataset.

Basic authentication: Power BI supports multiple authentication methods for connecting to data sources. The available methods depend on what the specific data source supports. Basic authentication, which uses a username and password, is a common method supported by many data sources, including OData feeds, web APIs, and certain databases. Since it is a possible authentication method, the statement "You can use..." is true.

On-premises data gateway:

Microsoft Power BI Documentation, "What is an on-premises data gateway?". This document explicitly states, "The gateway is required if your dataset uses one or more on-premises data sources. The gateway isn't required if all of your dataset's data sources are in the cloud."

Data Refresh:

Microsoft Power BI Documentation, "Data refresh in Power BI", section "What can be refreshed?". This page clarifies that datasets using Import mode need to be refreshed to get updated data. It states, "When you refresh data, Power BI must query for updated data from the underlying data source and then load the updated data into the dataset."

Authentication Methods:

Microsoft Power BI Documentation, "Power Query OData feed connector", section "Connect to an OData feed from Power Query Desktop". This article lists the authentication options for the OData connector, which include Anonymous, Windows, Basic, Web API, and Organizational account. This confirms that Basic authentication is a supported option for at least one common data source type.