Can I go back to a previous version of iOS?

My iPhone was damaged therefore I thought a iPhone 12 promax and the version was 14.5.1. My dexcom G6 is compatible with Apple version 14.3. I am told we cannot go back to a previous version. is there a workaround??. Dexcom cannot give me a time that they approve a 14.5.1

There will not be a fix coming from Apple for this. If a third party device is having issues with communicating after an update, that third party device also will need an update of some form in order to continue normal operation. If you have a third party product not working with your Apple device(s) you need to reach out to the manufacturer of that product for support.

Sorry, it is not possible to downgrade the version of iOS.

No. Downgrading has never been supported.

Did you find a fix for this? We are just getting started with our first Dexcom, and our phone has 14.5.1 on it.

So finaly is working with 14.5.1?