In theory. In reality, no. "I don't remember/I don't recall" is a famous dodge.
Yes but people can genuinely forget the exact words they spoke time ago, even one minute ago, or a whole conversation. Examples: Who did I talk to yesterday? Did I met that neighbor of mine yesterday or was it the day before? I don't know.
I think generalizing forgetting information ignores that certain conversations would likely have a better chance to be remembered