About: If I create a separate project for Report Library, then how to call any library report from UI project.
You can add a reference in the UI project to the Report Library. Then if you would like to display the report through some of our report viewers, you need to choose Select type report definition created in Visual Studio (Step #7 from Integrating the Report in VS App article).
You may also check our demos - they can be found in (Telerik Reporting installation folder)\Examples\CSharp (e.g. C:\Program Files (x86)\Progress\Telerik Reporting R3 2019\Examples\CSharp). The project is CSharp.WinFormsDemo. The Windows Forms viewer displays reports defined in the CSharp.ReportLibrary project.
About your last question:
You may use another Table/List to display the data from the other data source. Note that you can add a table in the Report Header section but not in the Page Header. To show the Report Header, right-click outside the report area -> Report Header. For more information refer to the Report Structure article.
You can also check the attached report which demonstrates the approach.
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