How to cancel a CR and what are the implications?
There are two aspects to consider: the workflow/CR status and the object versions. The workflow/CR can easily be canceled by someone with that permission using the button in the upper left of the Task page. Once canceled it’s still available for historical purposes and could be reopened or physically deleted using the CR Reopen/Delete component (see: Phire Architect > Change Requests > Reopen/Delete CR).
The object versions are something to possibly consider depending on how much work was done within the CR. If for example the CR had been migrated to TEST, then you might like to “rollback” the migration in TEST so that those changes are undone – you can do that through the “Rollback” button on the Migrations page. If that button is not available (because no baseline was taken), then you can create a new version set from PROD and ad hoc migrate that back to TEST to restore the original production objects. Likewise, you might like to restore the original objects to DEVL so that new development could start without any residual changes there. You can also do that by performing an ad hoc migration back to DEVL using the same baseline version set. Ultimately, how you handle this will depend on the specific CR, how much work might have been done, and what needs to happen with those objects next.