In general terms no there are 8, 10, 12, 16, 20, 28, 32 and .410 (67 gauge) although if the gun is from pre- 1910 almost every gauge imaginable was made by someone during the mid to late 1800's and a few oddballs up until 1910. There are some 6 and 8 gauge that were referred to as punt guns that were made to mount to a boat for shooting birds but they are also uncommon.
Custom build nowadays
No such thing as a 22 Shotgun.
If you can find one, yes.
Yes
Tough question, the Remington model 550 is a .22 rifle not a 12 gauge shotgun.
Not a thing
no serial noreg
mite check guage 20 or 28 guage
No. There are, however, .22 caliber shotshells made for rifles.
Pretty much a custom proposition. Do a google search on custom shotgun makers and start making phone calls.
Yes. The Mossberg 500A1 is a .12 gauge shotgun.
To determine exact value of a 1904 Marlin 12 gauge pump shotgun, you would actually have to take a number of factors into consideration. The main thing to consider would be the condition of the shotgun.