343 Guilty Spark(Level 6) (Where you're in the swamp with rain)
The Library(Level 7) (When the Sentinels still like you and you follow the Monitor to the Index)
Two Betrayals(Level 8) (Where you go to same three different snowy canyons in Level 5 except backwards and it's nighttime, and you destroy 3 Pulse Generators to buy time from the Monitor and the Sentinels when Cortana talks Master Chief into hating them)
Keyes(Level 9) (It's where you're in the same place as Level 3 and once again you're in the main Covenant ship and outside before you're on it again to locate Captain Keyes but turned into a nasty flood victim (just like the Pillar of Autumn but the Covenant version)
and The Maw (Level 10) (It's where you're in the Pillar of Autumn when it blew up and when you have to drive a Warthog really really fast to Echo 419 then the Pelican blows up and you have to drive again to get to a spaceship of some sort(don't know name of it) before time runs out)
The Flood isn't introduced until Level 6.
You have to get through several levels then you work with the aliens to defeat the flood.
Yes, there are three Easter egg levels in Halo 2
you cannot be the flood in halo
HALO Wars has the most levels. But if you're just talking about the regular first person HALOs, then HALO 2 has the most levels.
you can't
Be player 2 in the halo 3 co-op campaign. Or, play the Arbiter levels in halo 2.
no the were only on halo rings
You cannot see the Pillar of Autumn in Halo 2 because it exploded when Master Chief detonated it to destroy the Halo ring and the flood and covenant on it in the first Halo game.
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.