Practice conditions depend on the state. Many, if not most, states require at least one year of residency + all three steps of USMLE/COMLEX before granting an unrestricted license to practice medicine.
In addition, most third-party payers will not pay physicians to perform primary care who have not completed a residency in primary care (peds, family medicine, internal medicine) and most hospitals will not grant admitting privileges to physicians who have not completed residency.
Thus, a person may be able to get an unrestricted license after one year of residency but would have to open a cash-only type practice and would not have hospital privileges.
Just graduating from medical school generally might get you an MD or DO but what's the point unless you can practice (takes license and residency)?