A family of Microsoft word processing software products for creating web, email, and print documents.
In both Word and Excel, the preview is in the Backstage Print view (File > Print):
You can open multiple documents in Excel, as long as they do not share the same file name. For example, trying to open an Excel file called "test" which is saved in the Documents folder will fail if you already have a file called workbook called "test" open (stored on the desktop, say).