Before all the votes had been counted in the last election, he rushed to announce his candidacy.

[Beastly Boy]

3. What would be the justification for Garland ro appoint a special counsel in March of 2021?

There are specific justifications written into law under which an AG can even consider appointing a special counsel:

CFR § 600.1 Grounds for appointing a Special Counsel.

The Attorney General, or in cases in which the Attorney General is recused, the Acting Attorney General, will appoint a Special Counsel when he or she determines that criminal investigation of a person or matter is warranted and—

(a) That investigation or prosecution of that person or matter by a United States Attorney's Office or litigating Division of the Department of Justice would present a conflict of interest for the Department or other extraordinary circumstances; and

(b) That under the circumstances, it would be in the public interest to appoint an outside Special Counsel to assume responsibility for the matter.

What conflict of interest could Garland claim before November 15, 2022, when Trump announced his intention to run for President?

Us debating anything doesn't change federal regulations.