ISI publication.
This means publishing your works in ISI approved publications. If your submission is rejected, there's always feedback from rejection. Normally:
1. Minor rejection, touch up some things, redo some things. Then editor would reassess again. There's no need to restart the submission process.
2. Major rejection. Editor/peer review believes your submission is not up to standard. You'll have to redo your manuscript and restart the submission process from beginning.
3. Editor asks you to publish in other journal. Maybe your submission does not meet the criteria of that publication.

Presentation is different than publication.

You must always refer to your offer letter. In it will be requirement for your graduation. How many paper you need to have. how many international/local conference you must present, if you need to present at all.

Viva.
Viva is a test of your knowledge on the subject you are pursuing. Sometimes it's a critic of your analysis method or output.