What happens to expense report if they are returned from actions in manage expenses

Hello,

We import expenses from a third party application. we need your help to understand how to delete them from oracle expense module if we identify those as duplicates, is there a mass deletion feasibility from oracle?

Also what happens if exercise option from actions to return expense reports, where can we see that in oracle fusion? since these are coming from a third party and the user is not entering expense within oracle, how can we ensure with this option that where the expense report went?