You can create a new QuickBooks Online (QBO) company, and close your current one.
Once you cancel your QBO subscription you have read-only access to your data for one year. Then, on your new account, you have the option to move your Chart of Accounts. Here is a link to walk you through the steps: Import your chart of accounts to QuickBooks Online.
However, if you'd want to reconcile multiple months, you can do so by doing them one statement at a time starting with your oldest statement.
For additional information about the best practices when doing a year-end reconciliation and the steps on how to do it, I'd recommend following these articles:
I also recommend getting in touch with an accounting professional for more expert advice. Every organization is unique and they can make suggestions on how to handle this. Our Intuit Find-A-ProAdvisor site allows you to find certified professionals in your area that have the answers you're looking for.
Let me know how this goes and if you have additional questions. I’m more than happy to help. Take care!