I have a requirement need to Cancel case any time in the Case Life Cycle, my idea was to add as optional action- eventually is become cancel local action in case lifecycle.
But thought of utilizing OOTB Approve/Reject , My Question is during different case stages - one of the stage step I added Approve/Reject then is getting as Alternate Stage "Approval Rejection" , my question is it available whole case life cycle?
Then what is the difference adding as optional actions ? and using OOTB Approve/Reject?
The button-launched local action I described earlier can be configured as a case-wide local action which is your option (3).
Your requirement is to be able to cancel the case at any step. Approval is step within a Primary stage.
You can always implement a variation of the case-wide Change Stage action that jumps to a "Cancel/Withdraw" Alternate stage. There is nothing magic about the Alternate stage generated by the Approval step - you can create it yourself.
If there is an elaborate process required to cancel a case, then option (2) would make sense. You could also implement that process within "Cancel/Withdraw" Alternate stage step(s).