InfoPath Dev

I Like option two, but what would be the condition rule? How would I set that rule? 

Yes.. All fields are mandatory.. once users click on submit they should get an pop stating which fields are left blank

I have a form created with many fields which are mandatory. I want a validation to be done on the sheet for all fields before it has been submitted. Also looking for a customize error message which says which are the fields which are left blank Can someone help me on this?