Immigration Site

I will have an interview on Jan.13th and I plan to go back to my homecountry on around Jan.24th.

If I get approve during the interview and get stamped on passport, does it mean that I can travel immediately?

If after the interview the interview officer does not say whether I am approved or not and saying I need to wait or IO says my case is pending approval for security check, can I still travel with AP? Or do I have to get green card and stamp on passport in order to travel outside this country?

Thanks,