One eligibility requirement for this OPT extension is that the student must apply on time (at least 90 days before the current post-completion OPT expires).
Accordingly, if an F-1 student's OPT expired and failed to apply for extension on time, he or she may not be eligible for the additional extension.
After the grace period, you are no longer an F-1. Your pending change of status application can only keep your current status lawful. You need to get it approved in order to be authorized to work.