Walther
Bersa, Berreta
Iver Johnson was the manufacturer.
A week or so
Fegarmy Arms Factory Ltd (Budapest, Hungary)
FIC was an importer, not a manufacturer.
Herter's was an importer, not a manufacturer. No published sn data on what they imported.
It depends on the brand and model. Check with the manufacturer for an owner's manual.
Internet searches, Blue Book of Gun Values, library, manufacturer of the weapon.
You can find extra cylinders for a Titan Buffalo Scout handgun at gun shops, online firearm retailers, or directly from the manufacturer's website if they offer spare parts for sale.
Normally, you can't with any assuredness. The serial number itself won't normally reveal the manufacturer.
As far as taking it apart, it depends on the model. Check your user manual. If you don't have one, call the manufacturer.