I still maintain that they were plotting a GFIV. Thank God they were uncovered. But those are the questions I would have asked.

However, if the policeman had not entered the bar, would Aiello have released the garrot anyway. If he did, then Frankie would have probably survived to testify against Michael. On the other hand, given that Frankie was elderly, his near-garroting and being dragged by the neck to the rear of the bar could have resulted in a heart attack or any number of afflictions that would have precluded his testifying or made it an iffy matter.