Forgot old passcode and now can't access previous data.

A couple months ago, I mistakenly changed my iPhone passcode from 4 to 6 digits and later forgot it and was locked out. I had to delete my iPhone and started over by installing from a back up. But now, I can't fully access some previous data or update properly across devices connected to my Apple ID unless I sign in with that previous 6 digit code first. What can I do? Im prompted to reset end to end encryption. what effect will that have? I don't mind loosing some data if it means I can keep my ID and update devices properly.