Yes, if the data requested is not available by the due date, your best estimates are an acceptable substitute for actual data.
Yes, we always want to improve our data. You can submit revised figures via our Secure Messaging Center (SMC), which can be found on the left hand side of our Business Help Site: https://bhs.econ.census.gov/bhs/qfr/index.html
In order to reflect these changes and provide users with the most accurate data available, revisions are made to the most recent four quarters of previously published data.