Error When Customizing Opportunity Form

Hi all

I am using CRM 2016 online and below has been my source of pain for the last 4 hours..

I added to simple fields on the opportunity form - a Boolean and multi text field, saved and published and now cannot access any of the opportunities. I then thought i could go to the form and remove the fields to see if this was the problem but alas, I  get the same error when trying to access the opportunity form. I have even tried to add a new form on the opportunity entity but the error persists. The error just says..An error has occurred, contact admin blah blah.

At one point i was able to download this log file but its all Greek to me. Anyone else encountered such and is there a way to resolve this. I have tried importing a vanilla opportunity entity from another solution but still no joy.

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #20B1B7E0Detail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ErrorCode>-2147220970</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #20B1B7E0</Message>
<Timestamp>2016-08-12T20:29:09.2997969Z</Timestamp>
<InnerFault>
<ErrorCode>-2147220970</ErrorCode>
<ErrorDetails xmlns:d3p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>System.NullReferenceException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #3631C489</Message>
<Timestamp>2016-08-12T20:29:09.2997969Z</Timestamp>
<InnerFault i:nil="true" />
<TraceText i:nil="true" />
</InnerFault>
<TraceText i:nil="true" />
</OrganizationServiceFault>