Should you chamfer CPVC pipe before gluing?
About the only reason I could see to chamfer the end is that it would seat a mm or 2 deeper in the fitting. In that the glue is solvent welding the plastic, I doubt it makes a lot of difference in the strength of the joint. That said, I don't see that it would be a problem if it helps in joining unless you overdo it (like sharpen the end).

As far as I know, primer and sanding serve the same purpose - primer softens the surface and sanding gives more surface area.  Both of these improve the performance of the solvent.  Whether you need primer or not depends on the glue - there are single step glues that combine the primer and cement and there are two step glues that require priming then gluing.