Can I temporarily downgrade from Catalina

The greater problem is that Microsoft have disabled their activation servers for older versions of Office. I know from experience that is the case with Office:Mac 2008, and it may now apply to any unsupported version of Office, 2011 among them.

LibreOffice is a very mature and stable open-source productivity suite that reads and writes Office files. The only issues I had with it was that its 2018 version would import the text and text formatting accurately, but it did not so so well with Page Setup options.

Had I only a few Word files that needed this manual page setup correction, I would be using LibreOffice now. Unfortunately I have thousands of Word files going back to Word v3an v4, and there was no way to batch-edit the displaced margins. I now use Office 2019.

iWork is a nice option, too.

No. If your computer came with Catalina you can't downgrade it. But even if you could, you could not install Office 2011 then upgrade to Catalina and have Office 2011 work. 32 bit apps do not work with Catalina at all.