After rolling back to Windows 8.1:
I cannot logon using a Microsoft account
An App that was installed in Windows 8.1 but was updated in Windows 10 no longer works and cannot be uninstalled or updated
My internet access is working fine BUT there is always an exclamation mark stating there is "no internet access" or "limit access".
Did anyone experience the same problem or am I the only one that rolled back to Win 8.1?
The easiest fastest fix really is to perform a re-fresh of Windows 8.1. You will preserve personal data, documents and settings, but apps, drivers and such will be wiped.
I don't see a better way to fix all your problems — the way I see it, the rollback to Win 8.1 may not have been entirely successful (maybe a driver was incompatible, or your antivirus might have prevented Windows from making some changes) meaning you have a rather buggy OS — attempting to manually debug each and every issue would be time consuming and you'd be better off saving yourself the migraine and just re-do Windows 8.1 from scratch.