Raj asked: “my main quest is to understand if the concept of a soul was prevalent during the time of the Buddha”
– Yes. It was the concept of an “atman” (or “āthma“). You stated that you are familiar with Vedic teachings. What is the concept of an “atman” as you understand?
Once you answer that question, I will try to answer your other questions. I just need to figure out how to answer them so that you will be able to understand.