China
In what country?
Austria
US
This all depends on the country where you live. Some countries consider them firearms. In the USA they are not considered firearms but you must be 18 to purchase one. Other countries may not consider them firearms but they are heavily regulated.
United States.
You need to specify which country. We get questions from several nations.
Varies country to country but generally speaking having firearms for protection on civilan ships is not illegal under any international law. Now there is most likely a limit on number and size of the said firearms but that's another story...
The Chinese created the first firearms.
Firearms arrived with the Europeans, if by America you mean the United States, then the first firearm brought into that country would have been in 1513 when Ponce de Leon landed in St. Augustine Florida, carrying with him small cannon and the arquebuss, an extremely awkward and inaccurate matchlock smoothbore.
Matter of opinion- and you have to define "best".
YOu will have to specifiy if you mean in a country or the world.
The first rifled barrel is generally attributed to Germany. In the early 15th century, German gunsmiths began experimenting with rifling, where grooves were cut into the interior of the barrel to improve the accuracy and range of firearms. This innovation laid the groundwork for the development of more advanced rifled firearms in the following centuries.