1. What are the borders of Biblical Eretz Yisrael? And how do we determine them? 2. Why do we give preference to Talmud Bavli? Talmud Yerushalmi was written in Eretz Yisrael. Shouldn’t it be considered to be on a higher level? Shouldn’t Daf Yomi be strictly from Talmud Yerushalmi? Kol Tov

I am not sure what you mean by saying biblical borders, during the time of the bible there were numerous stages of our sovereignty and at each stage the biblical borders were different. There are the borders promised to Abraham, there are the borders Joshua conquered with the people, there are the borders of those who returned from Babylon after the Babylonian exile with Ezra the scribe, all of which have Halachic significance. You can see all the different borders and their sources in the Talmudic encyclopedia 2nd volume pp. 205-211. As for the Babylonian Talmud – since it was edited more than a century after the Jerusalem Talmud it is Halachacly binding as the rabbinic authorities of Babylon saw the Jerusalem Talmud and despite the earlier conclusion - disputed, it is the final halacha as ruled by a later authority. More so the Babylonian Talmud is written in a more explanatory way it is easier to understand.