Unless you work for Valve as a programmer working specifically on Left 4 dead updates, it's unlikely that you'll be able to alter the gameplay.
All you can do is change how you play the game.
Yes
No, Left 4 Dead 3 is not coming out. There is only Left 4 Dead and Left 4 Dead 2. Both fun games.
No, left 4 dead will only work for left 4 dead mods.
left for dead
They (Valve and Havok) haven't announced a left 4 Dead 4, but they have announced a Left 4 Dead 3 coming out in 2011.
Actually, no it is not a rip off of Left 4 Dead. Maybe Dead rising but not Left 4 Dead. Let me show you. Dead Island: It was originally announced at E3 2006 dates May 10-12 2005, but was pushed back to 2011. It was released on September 6, 2011 in North America and September 9, 2011 for PAL regions. Left 4 Dead: Development on Left 4 Dead started in Mid 2005, after the E3 release of Dead Island. Dead Island wasn't ready to be published in a 2 year swing of un-talented gameplay, and horrible CSS engines. They wanted to refine a game, not puke one out every year or so. Therefore, Dead Island was assumed by all to be a rip off of L4D.
You can't get The Passing on Left 4 Dead 1. It is only a DLC for Left 4 Dead 2.
Not Left 4 Dead 1 or 2, but Valve and Havok announced the Haggard in Left 4 Dead 3.
Left 4 Dead is quite a good game if you like shooting zombies in an online mmo style. But, if you already have left 4 dead, you should get left 4 dead 2.
If you love zombie games then you'll love Left 4 dead, they also came out with Left 4 Dead 2.
Steam's Left 4 Dead and Left 4 Dead 2 engines have eliminated bunny hopping.
get it online or from the local stores, http://www.allcdkey.com/Left-4-Dead-PC-Games.html, spend $29.99 for left 4 dead