Downgrade Office 365 Click to Run

First you going to need to know what you are downgrading too.

https://docs.microsoft.com/en-us/officeupdates/update-history-microsoft365-apps-by-date

Once you know the build you want to use:

1. Start PowerShell Elevated
2. Type cd  "C:\Program Files\Common Files\Microsoft Shared\ClickToRun"
3. Type ".\OfficeC2RClient.exe /update user updatetoversion=16.0.<BUILD NUMBER>"

This should then trigger the Office installer which will do the rest of the work.  Once its finished I would open an office application and confirm its worked and then disable updates.

I would not recommend this as a go to fix really if you can help it.  but if you have old add-ins and plugs that are playing up on a newer build and the company is not in a position to get them updated it can help in the short term.

Long Term I would recommend resolving the issue that is that is making you downgrade and then reenable the updates again.