re: Early start
I freely admit I was nowhere near Venus in the last few billion years,
but I get the feeling that even 2 billion years for the planet to maintain
serious amounts of liquid water were not enough to develop any really
complex life forms, especially the kind that could escape the planet
before it turned into the acidic roaster oven we have today.
Now if you mean some of the simple life forms may have escaped via
giant meteorite impacts, or somehow drifted high up into the planet's
atmosphere and caught a ride on some cosmic rays, well....