VZ 58 is the family name of these rifles. I think your thinking of the CSA rifles with tabbed bolt carriers. The trigger groups in the CZ-858 do not have the auto sear that their full auto siblings have, only a simple disconnector that is not engaged fulltime while the bolt is out of battery. It can cause an issue called the gremlin where the shooter accidentally pulls the trigger during action cycling, pulling the sear down which lets the striker travel forward with the bolt and light strike the primer rather than catch on the sear to be released when the trigger is pulled and hit with enough force to ignite the primer. The tab holds the disconnector down so the sear cannot move until the bolt is almost locked. Thus preventing the gremlin. As to your second question, could you be more vague please? It all depends on the quality of red dot and the mount you use. If your a cheap ass who still thinks saving money on optics is actually saving money then no, your NC star will get its bell rung and die. If you believe in paying for a little quality and mount it properly then yes, it will hold zero just fine.
