By Nate Raymond and Joseph Ax

NEW YORK (Reuters) - Steven A. Cohen's SAC Capital Advisors hedge fund pleaded guilty to fraud charges Friday as part of a $1.2 billion deal to resolve a long-running insider trading investigation, but it did not completely resolve the certainty of the fates of the firm or its principals.

Adding a layer of complexity to the plea, the judge on the case reserved her decision about whether to accept the plea until after reviewing the plea agreement along with a report prepared for the sentencing. (See Nussbaum's allocution http://static.reuters.com/resources/media/editorial/20131108/allocution.pdf )

The lead prosecutor also said had the case gone to trial evidence would have come to light of misconduct by more than just the six people who had previously pled guilty - and became the basis of SAC's plea.

At a court hearing in Manhattan, SAC general counsel Peter Nussbaum entered the guilty plea to four counts of securities and one count of wire fraud charges, a crucial step toward ratification of the fund's record insider trading accord.

U.S. District Judge Laura Taylor Swain said she would refrain from deciding about whether to accept the plea until after she read the pre-sentencing report. She scheduled the sentencing hearing for March 14.

"Financial institutions should know that they are not automatically immune from prosecution, and we will hold companies, as well as individuals, accountable wherever appropriate," U.S. Attorney Preet Bharara said in a statement released after the hearing.

As part of the plea, Nussbaum listed former employees who had been convicted of insider trading charges and described their offenses.

"On behalf of SAC, I want to express our deep remorse for the misconduct of each individual who broke the law while employed at SAC," he said.

"This happened on our watch, and we are responsible for that misconduct."

Ethan Wohl, a lawyer for investors in a lawsuit related to another pending SAC insider trading case, urged Swain not to accept the plea.

He called it a "no-admit" plea and said, "The proposed plea would let the defendants plead out without acknowledging they did what was alleged in the indictment."

He also said that the judge should not allow SAC to "cherry-pick the offense that will have the least collateral damages."

THE DEAL

SAC's guilty plea was a spectacle few people wanted to miss; in fact, Swain agreed to take the plea on her day off from overseeing a months-long trial of five former employees of Bernard Madoff's defunct hedge fund. The courtroom was full to the brim, with senior officials from the Manhattan U.S. Attorney's Office lining the back, surrounded by various deputies.