all multiplayer is free...it only isn't when ur talking about live...
There are no CPU players for multiplayer in Halo Reach.
Yes
go to Marketplace, Game add ons, map packs, browse 'halo'
by getting xbox live
Yes, there is i played it with my Brother tons of times.
no it'll take place on the planet reach which is where Spartans were trained and when the covenant invaded it don't know about the multiplayer.
Bungie never brought it out. However, if you REALLY need it. Contact Nintendo or Bungie.
you can't make a firefight map using forge, only mutiplayer
Halo multiplayer is when you play Halo against a human opponent. There are several modes, including but not limited to Capture the Flag, King of the Hill, and Slayer. There are also various changes you can make to the gametypes.
Yes, if the achievement doesn't specifically ask for you to do it on a certain map then you can do it on any map, also if it says you have to do it on a certain game playlist (e.g free-for-all) then you have to do that.
no
You cant lower your weapon in multiplayer you can only do it when you change your network settings to local.