You can't, as far as the community knows so far.
Yes
Bungie has not revealed it yet but Probably yes.
Halo Combat Evolved was the first game to feature the Flood. They are first encountered in the level 343 Guilty Spark.
An ancient race that built the Halo rings and the Ark in order to starve the flood. It is revealed by 343 Guilty Spark that humans are descendants of the Forerunners.
A special feature from the Halo 3 Legendary edition. It is a report from 343 Guilty Spark describing each race, their alliance, howeworld, and their current population.
He goes BOOM. You have to kill him and... [SPOILER ALERT, SCROLL DOWN TO SEE] Escape Halo. [/END SPOILER]
In Halo 3, 343 Guilty Spark tells the chief "You are the child of my makers, inheritor of all they left behind. You are forerunner"
That is a mystery that no-one knows. There are only three survivors of the destruction of installation 04: John 117, the master chief, who escaped on a Shortsword bomber 343 Guilty Spark, the moniter of the installation, who simply floated away from the ring (as you see after the credits of Halo CE) and finally sergeant Avery Johnson
The game was supposed "to finish the fight" jhonson had his own story, so if he lived, the fight would continue
Sergeant Major Avery Johnson was killed by 343 Guilty Spark at the end of Halo 3. This was sorrowful moment in Halo and possibly one of the few times Master Chief even shows a glimmer of emotion.
If you mean the monitor on halo 3 forge then no, you cannot make the monitor use a laser. Only the monitor from the campaign (343 guilty spark) can use its laser, which it will do when prevoked.
You Get out of the Flood Prison on an Elevator where you find some Marines. Then you take them to a tower and you finish the level when a little round Robot teleports you away from the prison