Thanks for reaching out here. QuickBooks Online has the features you need in situations like this, without the need to open a new account as advised above . I'll be happy to provide more information so you're on the right track with your work!
I recommend reaching out to your accountant. They'll have the ability to undo all previous reconciliations back to the date for which you'd like to start over. This will allow you to ensure the beginning balance is accurate and you can reconcile in sequence with confidence. If you don't have an accountant, we can help you locate a ProAdvisor in your local area.
If you have any other questions, please don't hesitate to reach back out. We're always glad to assist!