Your question about Marinol (Dronabinol) is very interesting and will have an impact on an ever increasing number of people.
Marinol is a synthetic (man-made) version of THC the main psychoactive component of marijuana. It metabolizes, breaks down into THC-COOH just as naturally occurring THC does. (All of the ingredients of marijuana are called cannabinoids)
At the first step in drug tests (immunoassay) any number of cannabinoids can trigger a positive. The presence of COOH will create a positive. At this stage the test cannot distinguish one cannabinoid from another.
Generally, most drug tests for confirmation, second level when first step returns positive, are looking for COOH. Either Marinol or natural marijuana will create this metabolite. So smoked marijuana and Marinol would be indistinguishable on the standard drug tests.
However, the natural substance contains many other cannabinoids. In particular marijuana creates the metabolite THCV and Marinol does not. But detection would require additional testing or a special panel. (See Drugs of Abuse Testing, pp 138-139
) Many labs aren't set up to make this distinction.
Whether or not the marijuana is detected is largely a matter of the lab performing the test and whether the special testing is used.
As to the 4 beers, that should not show on an EtG test at that time interval.