Will my Microsoft Outlook and Excel stop working when my Microsoft 365 license expires?

Yes. "Subscription" in the software world has become a euphemism for rental.

The end of a "subscription" does not mean just the end of new updates (analogous to the way in which the end of a magazine subscription means the end of new issues). It means that you'll lose access to the software. Sometimes the software will run in a reduced-functionality mode so you can get your data out, but whether it does varies from vendor to vendor.

Maybe a question for Microsoft.

Yes.

That's how subscriptions work.

Also, any data you have in OneDrive that exceeds the amount you can get for free will be lost.

That appears to be a question for ⇢ Microsoft 365 Support.

Good luck!

Smiliñ 😎 Brian

Here is what Microsoft has to say about this --> https://learn.microsoft.com/en-us/microsoft-365/commerce/subscriptions/what-if-my-subscription-expires?view=o365-worldwide