Can I Return Back to the Destination Airport after I Diverted to the Destination Alternate?
There are no regulations in the US that state you must land at a particular airport. It will be even more difficult to find one that says you can return to your original destination after announcing or performing a diversion. There are only regulations stating that you have to list a destination airport on an IFR flight plan. And, that there are certain situations when you must list one or more alternate destinations on an IFR flight plan.
VFR flight plans are not required in the US. Even if you file a VFR flight plan, ATC will not be made aware of your flight plan unless it is not closed prior to half an hour after your ETA. In which case, only VFR aircraft on VFR Flight Following will be tracked by ATC. The pilot can cancel a flight plan (IFR or VFR) or flight following at any time that the pilot is in VMC, entering Class G airspace or landed. Otherwise, you must fly your filed IFR flight plan all the way to your clearance limit or your alternate (once you have informed ATC of your diversion). But, you may also amend your flight plan or Flight Following at any time.
Case in point. I have diverted to an airport just to take an unplanned bathroom break. Before diverting, I informed  ATC of the diversion as well as requesting to keep my flight plan and transponder (squawk) code. When returning to controlled airspace, I was able to continue onto my original destination.
Another example of continuing on to your original airport after diverting is when the diversion airport is en route to your original airport. Having an alternate airport planned that is halfway to your original airport gives the pilot a convenient out or Plan B if the weather ahead starts turning hazardous. If the weather improves before you reach your alternate, you can continue onto your original (after informing ATC if on an IFR flight plan or Flight Following).