a) would most agree that the origin of life began over 3 billion years ago?
Newly discovered stromatolites in Greenland have been dated to 3.7 billions years ago. Since these are evidence of the diversity of life at that period it proves that life began around 4 billion years ago. That's just a few hundred million years after the formation of planet earth.
It suggests that life is not a random event. It is probably inevitable on a geologically active planet.
b) if so then would we agree direct evidence for the origin of life impossible?
It depends on what you mean by "direct evidence". I think it will be shown step-by-step how life can emerge from geochemistry through unguided naturalistic means.
C) However am I correct in assuming the first cause of life had to be living?
No. Absolutely not. There is a continuum from geochemistry to biochemistry.