avi_suresh,
Just to clarify, responseId isn't really a counter; it's a static piece of metadata tied directly to the individual response. The number does increment up but again, it's not really a counter. I'm not sure if that's a hindrance to your end goal or not.
I did a quick test like so...

And that expanded Value...
{"webhookId":"98db531b-e63f-4f7f-ad77-fb7b2e38af98","eventType":"ResponseAdded","resourceData":{"formId":"<formId>","responseId":4},"eventTime":"2020-08-20T21:35:31.4458128Z"}
The reason you see that responseId is "4" is because it was my fourth submission of the Form. What you're also seeing is the full Body of the request, so that's all the metadata we have to use; no sign of anything that would be a proper counter.
If your Form is more like a quick survey (meant to be short-lived), responseId may work out just fine. If your Form is supposed to be in place long-term, though responseId may not be as effective.
To your actual logic, I don't think you need Get Response Details or Compose at all. Get Response Details can glean some additional data from fields in your Form but you don't need it for responseId and it still won't give you a counter. If anything, you're more likely to confuse your Flow's logic including it. Same thing with Compose, you don't have to set up any variables here; responseId is already solid.
I set up a Flow like so and it's working fine for me...

I hope this helps!
Sincerely,
Patrick