To put it as simply as possible when the forerunners created the rings they also created shield worlds. These shield worlds were refuges from the affects of the halo rings one of the forerunners informed the flood of this so the flood went to one shield world and survived on beings who were living there. Later the covenant discovered this world tried to use the forerunner fleet on the surface of this shield world the UNSC followed and got inside purely accidentally, as seen on Halo Wars. Therefore freeing the Flood. Hope that helps :)
THE halo games that have the flood are halo combat evolved,halo 2,halo 3 and halo wars
halo 1,2,and 3
No.
The Flood was actually contained inside Halo before some Covenant set them free. Their actual origins are unknown.
its possible
That is classified
An alien species that takes over the bodies of other creatures to survive
you cannot be the flood in halo
THE halo games that have the flood are halo combat evolved,halo 2,halo 3 and halo wars
no the were only on halo rings
halo 1,2,and 3
No.
No, there is no flood in Reach. With the expception of halo wars the flood was not released until halo combat evolved where the humans stumbled across their existence in search of a lost platoons distress beacon.
No. You can never play as the flood.
the flood is a virus which takes over dead bodies
Yes.
you can't