QuickBooks Online Accountant (QBOA) is really a portal to access client QBO companies. QBOA also comes with one free company (QBO plus level) that the accountant can use for their own business. The Accountant Tools menu (the briefcase icon) displays few specialty tools not found in QBO.
So, you do not need anther QuickBooks software to use QBOA. The client will invite you as an Accountant from their QBO. You accept the invitation to add to portal to access client file.
Undo bank reconciliation feature is not available in any plans at this time. It is available in Accountant version only.
In order to UNDO IT, first log in to your QBOA account
Go to Client home page screen
Click the company gear (upper right corner)
Click Reconcile under Tools
Select Bank Account to UNDO reconciliation
Hover your mouse cursor over the reconciliation month you want to undo (under Ending Balance or Auto Adjustment or any column) and as you are hovering you will see UNDO button to the right next to Auto Adjustment column
Select UNDO button
New Undo Reconciliation screen will open
Next, Success screen will open
Click OK again
It will longer be on the Reconciliation History & Reports list.
NOTE: If you need to sign up for QuickBooks Online Accountant version, you can do it from here and the price is right (it’s FREE):