Factual answers to the questions:
No sovereign independent country called Palestine has ever existed. The region was the British Mandate of Palestine (1920-1948), a League of Nations administrative territory, not a state. After 1948, the West Bank was under Jordanian control and the Gaza Strip under Egyptian control.
Israel captured Judea and Samaria (West Bank) from Jordan in the 1967 Six-Day War. Jordan had seized it in 1948 and annexed it in 1950; that annexation was recognized by only the UK, Iraq, and Pakistan. Jordan renounced its claim in 1988.
Israel is not occupying territory of any prior Palestinian sovereign state. The areas are disputed territories with competing historical, legal, and security claims.