I have multiple requests in one session, how to stop or cancel the request which is running but not stop or cancel the whole PhotogrammetrySession?
If you call cancel on the session, the current batch of requests is cancelled, and you should monitor the session output for a "processingCancelled" state before submitting a new batch of requests.
There is no api to cancel only some of the requests in the current batch, please file an enhancement request using Feedback Assistant.