And there is a planet of fore runners in another galaxy with an ancient forerunner battle fleet, the last battle between forerunners and precursors. So the precourser that was put in a time lock on charum hacor ( spelling?) he is the one that turned the mendicant bias evil and my question is is that precursor flood himself? Because in the book humans would go in to the facility and some would come out infected and some not

The precursors were not the Flood. The precursors created the Forerunners as slaves. The Forerunners rebelled and assumed the mantle. The Flood are a bio weapon developed by the precursors. The Humans accidentally stumbled across it and it slowly evolved and infected their "dogs". It eventually became known as the shaping sickness by the humans and the flood by the Forerunners. The gravemind Mendicant spoke to was a precursor mixed with a variety of other species.