How to reverse-engineer SQL statements issued by a legacy application I am re-writing the question below to provide more details.

We have a legacy application and are now developing it using a new technology. The database is SQL Server 2014. We know 90% of the tables that get updated when an operation is performed on the UI. However, we are not sure if we have covered all the tables. 

The customer wants us to run a scan of the database on the old system when an operation is performed on the front end and then do the same with the new application. HE would like to make sure that we are touching the same tables in the old and new application.

So, I would like to understand if there is some query I can run that will give the list of tables that were updated when I perform an operation on the front end. All the tables have last update date and user who performed the update.
You can setup a test database and trace the application activity using the SQL Server profiler. By tracing the event "Security Audit\Audit Schema Object Access Event" you can effectively trace all the SQL the client is sending to the server.  But that will not necessarily help you in discover the application logic.