Yes, they do.
Not very high dollar firearms, but not junk either. Basic, utility grade handguns. They DID make some very nice target rifles at one time.
Units who want to make a display of them are able to, with approval, but individual soldiers cannot do this. In Iraq, NOTHING could be brought back as a war souvenir - not firearms, not flags, nothing. Firearms, definitely not. IIRC, a soldier in the Minnesota National Guard tried bringing back two AKs. He was caught, and sentenced to ten years in federal prison.
No
One
Well, you must have a license for handguns first off. If that is good, then I think it might be okay... but to make sure, I'd suggest seeing: http://ag.ca.gov/firearms/
Inexpensive
Marlin doesn't manufacture handguns.
They did not make firearms. They contracted with makers of firearms to put their name on the firearms they bought.
Companies that make firearms, ammunition, and components of ammo.
As much as you want. Whether someone will buy it is another issue. RG handguns typically don't bring more than 15-50 USD. RG didn't make firearms long enough for them to be condiered antique.
No. Several companies made guns for Sears under the JC Higgins name. They still exist but no longer make guns with the JC Higgins name.