[SalesForce] Sending out email alert during business days

If this is a specific example, you can use the Email Log to see all emails sent by SFDC on the day in question to verify it was sent.

You have some other options as well

a) Add a Task to the target object that is created the same time the Email Alert is sent. The Task acts as a proxy for the email with respect to easy logging/verification

b) Enable Enhanced Email . Email body will appear in activity history.

Rather than searching and deleting interview records, you can run a SOQL query where due date is on future date where those interviews have been queued.

Run a DML update operation on the Grant_Report__c records and because of this update it will re-evaluate the process and previous interviews will be out of the queues and new interviews will be queued.

You can quickly test at your sandbox before moving it to production.

How do I make sure these would be on the new criteria?

Since you are making changes to the process so it will create new version and after updating all the records, new pending and waiting interviews will get created.

You can monitor those upon reaching Setup->Flows and then Paused and Waiting Interviews.

Here is an example taken from my DE

For more information, refer Monitor Your Processes’ Pending Scheduled Actions

If you still need to delete all pending interviews then write a SOQL query to retrieve records based on InterviewLabel with other suitable criteria and delete those.

FlowInterview fiObj = [SELECT CurrentElement,Guid,Id,InterviewLabel,IsDeleted,Name 
                       FROM FlowInterview
                       WHERE InterviewLabel = 'Sent_Email_after_case_creation-1_InterviewLabel' LIMIT 1];
delete fiObj;