1. Can I write a Form rule on Sales Order DFF in which if on certain condition i want to popup a message asking users to fill DFF Filed information at the time of booking?Yes this can be done using PCG Form Rules.
2. Where can i find the list of tables in GRC module? Is there TRM document?There is no such document available. You would want to open an SR to see if documentation is shared
3. I want to know when my flow rule last run? ( I want to know how to check it from the application and also from the back end tables)PCG Flow Rules piggy backs on Oracle Workflow. You should be able to verify as you would other workflows using Oracle Workflow.