How Can I create invoice processing flow and validation agent in UiPath. Can we create extraction part using DU in Studio On-pemises and pass extracted variable like invoice number, date etc or is it only possible with studio web? Can I Pass as an argument in UiPath? How Can I update status back to in Excel or queue? Can I know how to integrate whole flow? How to handle exception in Agent?
This is a broader question but I will try to answer.
Any rule based steps in your process you should be doing them in an RPA workflow or other features except Agent. You can use Studio Desktop as well as Web.
Yes you can
Use Escalations
Refer this article - Handling Exceptions in UiPath Agents: From Errors to Intelligent Recovery - Accelirate