General help

Hello, i know this might have been brought up before. but now i'm having a different scenario.
thing is i created a course with a certain criteria for users not to be able to complete it unless they complete " certificate " activity by viewing the activity as it would be automatically marked as complete.
i also set restrictions on that very activity to be hidden unless certain activities are completed first then the certificate would appear. so far that sounds reasonable. for some reason i had to hide the " certificate" entirely as we were not sure about the certificate design and we used to issue the certificate manually to users upon completing needed activities. now that we have agreed on the design . we need to use the certificate activity on moodle again. with the pre-fixed restrictions applied. problem is now that we have almost 300 users who completed the needed activities for the certificate to appear once we put that back to " show " they would be able to request new certificate which will cause some issues with duplication. so alternatively we thought about gathering all these users and put them into a group and make that " certificate" activity invisible for the whole group. and then the rest of the users can proceed normally obtaining the certificate on moodle. the real challenge we're facing now with the 300 users as we need to mark " certificate " activity as complete so they can complete the course.
is there a way i can do this in bulk or even in the back end like editing a certain file or something ?

sorry for the long post