My only recommendation is to do a Time Machine backup before you update, disconnect the hard drive or device you just backed up to, and then update your system. After the update, check to see if your QB is working. If it is not, immediately restore back to the Time Machine backup and decide how you want to go about your accounting needs. You could freeze that laptop and use it for accounting purposes only or some other solution.

The advisors here in this thread will only provide you with the currently supported version answers, which all require a subscription instead of a one time license fee.