God dealt with Abel as an individual, then turned to Cain and dealt with him as an individual. Some scholars argue that the difference between them was that Abel's was a blood offering involving a death, and Cain's wasn't. That may be the reason, but the Bible doesn't say that. We know that the Jews offered grain offerings later in their history. There was something on the inside that the Lord saw and that distinguished the two brothers.
Restoration is possible.
The problems you have on the inside, the rebellion that has led to your making an offering unacceptable to me, can be reversed. Relationship can be restored, things can be put right. But you have some very important choices to make. God spoke directly to Cain, but Cain didn't listen. He murdered his brother.