Is Israel an “occupier” of Palestinian land? Who owns “from the River to the Sea”?

Is there such a thing as the country of “Palestine”?
What are the halachic borders of Israel?
Is it mutar to give the Gaza Strip back now that Israel has retaken possession of it?
Is there a mitzvah to be buried in Israel? To make Aliyah? To exhume a body to Israel?
What does international law say about the West Bank, Gaza Strip and Golan Heights?