Requirement 1:
Consider we have Epics and Stories in our project.
As soon as we link Story to the Epic, we need custom field (say Project ID) present in Epic to be inherited in Story.
Requirement 2:
As soon as we update/change the custom field (say Project ID) in Epic, the same Custom field should be updated/changed in all linked issues, sub-tasks, linked issue's sub-tasks.
Thanks
Vinay