You build a factory
You cannot play as Covenant in the original Halo
NOPE
Yes, in Halo Wars you will be able to play as the Covenant. I dont know, however, if you will be able to play a story mode as the Covenant, but I know that you will be able to in Free Play and Xbox Live.
i believe you play as covenant in halo 2 because i think they wanted to give you something different in it and the story wouldn't really make sense if you didnt play as them.
Probably not ONLY covenant, but Halo 2 already has about half of its levels where you play in the life of the Arbiter, one of the Elites shamed after losing the first Halo ring. Both Halo 2 and Halo 3 allow you to play as an Elite in Multiplayer, and Halo 3's co-op allows you to play as the Arbiter for the second player. I hope this answered your question.
no
Not exactly. Instead of a Halo "4", Bungie have decided to release Halo:ODST. This game bridges the gap between Halo 2 and Halo 3. You play as an ODST marine in the game. Also, for RTS fans, Bungie have also made Halo Wars, a strategy version of Halo, in which you can play as either the marines or the covenant.
You can play only two different Species. The Humans, and the Covenant. The Flood and Rebels an only be played by A.I.
No. The Flood is controlled by an AI (Artificial Intellgence). However, you can play as the Covenant in Skirmish.
You can't, at least not on the Xbox version of the game. The PC version may be different.
Halo 2 is mostly set through out the game based on another Halo ring where the covenant have moved to. It is also set at the start of the game when you can pick up your controller and play as master chief on another human ship with different soldiers to fight against the covenant and stop them from boarding and planting a bomb to blow it up. Master Chief then visits Earth to stop the covenant there and then chases them to another halo ring to investigate. You play as the arbiter where he has to defeat the heretic leader and hold back the flood visiting two ships then he visits the ring to stop the brutes.
You can't unfortunately, but that would be hilarious and fun if you could! The only playable covenant in Halo Reach is the elite. Lets just cross our fingers they let us play as grunts in Halo 4 which is coming out Holiday 2012.