You will have to tell us what you want to use it for.
Korth
Have it examined by a gunsmith first. NEVER FIRE AMMUNITION IN A WEAPON NOT DESIGNED AND CHAMBERED FOR IT!
It will accept 357 magnum or 38 special ammunition.
No.
Fire ammunition.
Yes
Yes you can. The casing of .38 special shells is a mere .10 inch shorter than a .357 magnum shell and will fire easily in a .357 revolver. I've owned a .357 revolver for years and shoot .38 special ammunition in it all the time. Side note: Don't try it in a .357 semi-auto pistol (like a Desert Eagle.) At best the gun will jam and at worst it might cause an unsafe pressure build up.
Yes
.357
A pistol rated to fire .38 +P ammunition is still going to be a .38 Special pistol, and can use regular .38 Special ammunition. .357 Magnum revolvers are also capable of chambering and firing .38 Special loads - regular, +P, and +P+ included.
Yes.
357 sig is a cartridge that is a relatively high speed handgun round. It is not a pistol itself, many, many pistols are chambered for this cartiridge.