But let's examine what you're saying. You said in your prior post,
At the time that Genesis 4:7 occurred Cain was already a sinner who possessed the sin nature. So at that point he did not have the volitional will to “do good” in the sense that we are talking about.
Well then neither did Abel.
It is true that he was being told to make a choice between right and wrong, but his nature showed that sin and its consequences was real.
Abel had the same nature that Cain had when it comes to what they inherited from Adam.
In that sense Cain is no different than me or you. We are told to observe God in obedience and follow his commandments, but we will fully knowingly choose wrong instead of right all the time.
Abel wasn't morally perfect either yet he made a right choice. So looking at how you argue your case, IF I'M READING YOU RIGHT you have God make a statement to Cain, "Will you not be accepted if you do right" but you don't let that mean that he can. It's like you have God tantalizing Cain, building him up for an expectation and an end result he can rightly achieve but going away from and having God say but no I'm not going to give you the ability to fulfill that end result I'm exhorting you about. You do know that is creating a potential end result for Cain to consider? If not why did God say it?