First created in the 1400's, and we do not know who the first gunmaker was that cut grooves into the bore. It seems to be European in origin, and MAY have come out of what is now Germany, but that is really a "best guess".
Neither barrel is rifled.
Not safely
You look down the barrel and if it is swirled it is a rifled barrel and if it is not swirled it is a smooth bore
Shooting rifled slugs is the ONLY way to shoot thru a smoothbore for deer. If you shoot sabot slugs thru a smoothbore, it will not spin and therefore not be accurate. For accuracy, the slug must spin out of the barrel. Either shoot a rifled slug thru a smooth barrel, or shoot a saboted slug thru a rifled barrel.
a slug is normally use in a shot gun and they are not rifled a gun with a rifled barrel should shoot a Shell that is the same caliber as the gun.
Smooth-bore refers to a firearm or cannon which does not have a rifled barrel (a rifled barrel is one with ridges that corkscrew down the barrel to impart a spin to the bullet)
Slugs! If its rifled it is a deer hunting barrel.
Rifles and pistols
Assuming you mean a barrel that is for lead pellets, if the barrel is not rifled, steel shot will not damage the smooth barrel. If it is rifled however, steel shot will in fact damage the rifling.
Yes it could be done, but you would have to locate a smooth bore barrel to change it with. Remember smooth bore barrels are not as accurate as a rifled bore barrel.
Look inside. If it has lands and grooves, it is rifled. If it does not, it is smooth
A rifled slug can be fired from a smoothbore barrel with relative accuracy to about 100 yards. By relative accuracy, I mean that shots can be held in a 5 inch circle. That is about the size of the target zone on a deer. For a rifled barrel, rifled slugs should NOT be used, but sabot slugs can be.