No you can download the game, you just have to find a working mirror, I don't think you will be able to play it anyways, unless you can do what you could do in WON days, and install mods under CS folder. Maybe someone can answer question about playing it with CS.
You cannot play since you do not have half life 1.
Itr is wrong in what he is saying - it sounds to me like you have halflife 2, and condition zero cdkeys and that is all.
If that is the case, then ESF will not work - you need half life 1.