Regarding the 'XXXX' marking, the previous replies are exactly right: that's how Kershaw/ZT marks their blems (knives that didn't pass QC). Again as already mentioned, it's usually for some minor cosmetic reason, but regardless of the reason they didn't pass QC blems don't carry Kershaw/ZT's warranty. If it was advertised as a blem or you got a good deal on it, I'd say keep it, but I agree with the above that if it was advertised as "new" or didn't say anywhere that it was a blem, you should consider requesting your money back (and, if you bought it through eBay/PayPal or someplace like that, filing a buyer protection claim if the seller refuses to make right).
As for the "G&G Hawk Design" marking and bolt/glass breaker, I think later 0500s came with the designer marking and without the glass breaker. So there's nothing there that raises a red flag. For the reasons already mentioned, though, the fact that it's a blem is something that you may want to pursue depending on how it was advertised, etc.