Surely Palestine has had more than its fair share of invasions, conquests, and occupations.
WWI was a turning point for Palestine. Palestine came into legal existence when it was separated from Turkish rule after WWI. Its land was defined by international borders. Palestinians were a nation of people distinct from their neighbors. The Palestinians were the citizens of Palestine.
The Palestinians had inalienable rights in Palestine, including:
(a) The right to self-determination without external interference;
(b) The right to national independence and sovereignty;
The only reference to foreigners is that external interference is illegal.
Palestine did not come into existence after WW1 it had been in existence as an area for 2000 years
The land of greater Palestine yes that includes what is now Lebanon, Syria, Iraq and trans Jordan
The arabs of Palestine were indistinguishable from their neighbours because that is were they originally came from
The majority of Palestinians were recent migrants, this is proven by the fact they changed the rules to accommodate the recent arrivals.
The exercised their right to self determination when they refused the offer of a nation in 1948. The only outside interference came from the arab league who invaded the land and tried to wipe out the Jews.
Unless you have an unbiased account that says differently of course, not the usual Palestinian one that adds details to existing treaties because he thinks they should be part of the treaty.