Yes, but it is currently under development.
There is a Half Life 2 Episode 3 coming in 2012.
Half Life 2 Half Life 2: Episode 1 Half Life 2: Episode 2 Portal Team Fortress Hope this helps ;)
You can't, but Half Life 2 Episode 3 supposedly has it.
no
you start with half life 2, then you play half life 2 episode 1, then you play half life 2 episode 2, so you are basically playing them in the order they are in at the game select screen (where you choose any of the half life games, portal or tf2)
a
Yes, they are all different games; episode 1 follows on from hl2, and episode 2 from one.
Garry's Mod requires only that you have one Source game.This includes Half-Life 2, Half-Life 2 Episode One, Half-Life 2 Episode Two, Team Fortress 2, Counter-Strike: Source, Half-Life: Source, Portal, and a few others.However, if you have Half-Life 2 Episode One, you will only be able to experience Half-Life 2 Episode One (and Garry's Mod) content. You won't be able to fight alongside Griggs and Sheckley with a home-made "Antlion Dispatcher", or be teased with cake while solving complex puzzles using the portal gun, physgun and toolgun.Long answer short, you should only need Half-life 2 Episode One in order to play Garry's Mod, but you can experience more of Valve's games in Garry's Mod if you have all of Half-Life 2.
9
Half-Life 2 Episode Two - 2007 VG is rated/received certificates of: USA:M
soon!
Well, valve said that it would come out on 2008/2009, and that never happend. So instead of making a half life 2 episode three, they planned on making a half life 3.