It's just a professional organization similar to, for example, the FACS you often see behind a surgeon's name. The FAGD title just certifies you've met a number of professional development criteria. There's a second title, MAGD (master), for those who meet an additional list of requirements. It's not a legal designation, it's just a way to outwardly identify yourself as someone who takes an interest in improving yourself professionally.
No, this is not the case. Someone can simply put those words with there name without doing anything. The FAGD denotes a specified membership period (it has decreased), certain number of CE hours, and a written test.
The MAGD takes significantly longer and is based on hands on CE courses in specified areas which a GP in the civilian sector rarely obtains prior to at least 10 years in private practice.
The easiest way to see it is to go to www.agd.org as another individual had noted.