For your other concern; define a triggering event with process builder and call the flow that creates Accoun, Contact and Opportunity records from it. Use your Record Create element for each object and reference new records' IDs with a variable, then link them together.
For your other concern; define a triggering event with process builder and call the flow that creates Accoun, Contact and Opportunity records from it. Use your Record Create element for each object and reference new records' IDs with a variable, then link them together.