Identify the Process instance ID of a cancelled process for re-triggering the instance

Assuming the canceled process instance hasn't already been archived, I think what you could do is create a report where your process model is the context that would contains all the necessary fields (in your case, at least pp!id) and add a filter that matches based on Employee ID.

Once you have the above set up, you can use the smart service called "Execute Task Report" (where the report I mentioned above you would have to create is the context) before "Start Process" smart service in a newly created process model to start that canceled process instance.

Note: If filtering on employee ID returns multiple instances, then you'll need an additional filter like something below:

1. not(isnull(process_completion_time()))
2. num_cancelled_tasks() <--- this is a process metrics function (will probably need more to do than just the function itself)

We have found it handy to retain the process id (pp!id) for some process models that are likely to run for a while in the database. When the process is created and we store the key data fields for the process/application in a CDT/database table we add a processid column to the CDT. By storing it in the database we can access it when needed for debugging or possibly sending messages to the process.

A few thoughts:
1) pp!id values can be reused sometimes, so you may want to consider setting the value to null in your cdt/database when you complete the process model and don't anticipate needing it anymore (so you don't retain legacy ids that may cause duplicates in the future)
2) the pp!id I believe is stored as an integer but sometimes needs to be stored as a text field I think, or maybe it is the other way around. just be aware of the data type that Appian sees it as in the reports, etc. You don't want leading 0's to be lost, etc.
3) we haven't restarted processes using this method I don't believe, but you probably would want to verify the process exists before calling the restart node smartservice, etc. I've found that some Appian functions are a bit finicky with null values and invalid values (for instance, if you have a user with a supervisor and the supervisor's account is disabled, the update user profile smartservice hiccups because of the essentially invalid supervisor.

The process report doesn't depicts all the active instances rather depicts only one instance. The filter and criteria are correct but I thought it depicts all the instances of that process but doesn't seems to the case. Any thoughts on this?

You most likely have a configuration issue with your process report, then. If you'd be able to post screenshots of your configuration details (report context, filtering, etc), we can probably help figure it out.

RPR Process Report.docx

Attaching herewith the extract from Process Report

Your bottom screenshot does seem to show multiple instances including a cancelled one - is that not what you're seeing in your report? You also didn't show the first configuration tab showing the report context / etc.