I'll just answer the second part since the first part isn't really provable (though Hinduism is recordedly older, and it's polytheistic still). A long time ago, there was a man named Abraham, who was the father of Judaism and Islam alike. According to different religions, he was either Hebrew (Jews) or Arab (Muslims). His first son was named Ishmael, and his second son was Isaac. Why I say Islam is derived from Judaism is because (this is what the Jews and Christians believe) God asked Abraham to sacrifice his son, Isaac (he didn't actually have to, but he was about to when God stopped him). Because of Abraham's devotion, he was promised stuff. Ishmael, presumably jealous because he wasn't the son God promised Abraham, left his father and brother with his mother the maid. He must've passed down the ideology to his children that he, not Isaac, was the promised son, the son destined to inherit greatness, the son that would father God's nation. As for Christianity, God promised the Jews a Messiah, and we Christians believe that this Savior is Jesus. However, not all Jews agreed, so Judaism and Christianity couldn't remain one religion. Hope this helps explain!