What effect does a concession on ineffective assistance of counsel have on the court's ability to adjudicate the merits?

QUESTION(S) PRESENTED ; (1) What effect, if any, does a concession made by the U.S. on an ineffective assistance of counsel claim have on the court's ability to ajudicate the merits? Conversely, does the concession render the issue moot? (2) Does a concession by the U.S. on an ineffective assistance of counsel: claim automaticly.satisfy the standard under Slack v. McDaniel, 529 U.S...473, 484 (2000), for obtaining a Certificate Appealability? (3) Should prejudice. be.:presumed when.an attorney fails to promptly notify the court of a conflict of interest or a breakdown in communication with his client; in the context of an ineffective assistance of counsel claim? (4) May the. court correct a plain error which affects substantial rights or the public reputation of judicial proceedings at any stage in light of.the law of the case doctrine? ~i . . *