Yes FoxHound, its like you said if I have 5 monsters in level one and I kill them, then I can proceed to the next level.
But I want player to be able to go back to the first level and complete some other tasks without having to kill those 5 monsters again.

So I have to ent_create("monster1.mdl", vector(10, 20, 30), monstersFunction);//(Ican't bring those 5 monsters throughout WED?) and define 5 different monster names and turn them into global var and set global vars to 1, then check them to see if they have been accomplished/removed and set their vars to 0?

I felt like this could be done by game_save and game_load each level, I guess not.