While many starters, such as the Protean Froakies, are available in friend safaries, I believe the hidden ability Serperior and the other 2 starters from the same gen were only available through events.

I do have a Contrary Serperior though, so if you need one, I can breed you one I suppose.

Also, no. You can't breed hidden abilities without actually having a hidden ability pokemon to breed with first.