I can’t speak for that specific game, but in general, the minimum requirements for processor speed are only so that you will have an acceptable frame-rate. Your game may stutter or lag if your CPU does not meet the minimum requirements for the game.
As for other requirements, if the game requires a 64 bit operating system and you try to run it on a 32 bit operating system, then the game won’t run at all. If the game requires a certain amount of RAM and you don’t have that much installed, the game might run and it might not, or it might run for a bit and crash.
Command and Conquer is an older game, isn’t it? That 2.0 GHz requirement is probably for an older single core processor. Modern processors are typically not rated on clock speed alone as that is a fairly meaningless number these days. Most games these days will give sample CPUs and say you need the equivalent of that or faster.