The 922 is a "pull pin" revolver meaning that the frame is one solid piece and to load and unload it you have to pull the center pin out, remove the cylinder, and poke the cartridge cases out of each chamber one at a time. Once the chambers are empty, fresh cartridge may be inserted and the cylinder and center pin placed back into their respective position in order to reload the gun. While slow to load and unload, revolvers of this type are comparatively simple and easy to manufacture and, as such, could be sold for very reasonable prices.
The 999, on the other hand is a "top-break" revolver with automatic extraction similar to the S&W Model 3 or British Webley. To load and unload this type, all you have to to is unlatch the barrel catch and the barrel/cylinder assembly will hinge downward. As the barrel hinges down, the extractor star will raise up out of the face of the cylinder and push all of the cartridges/cases out of their chambers to fall free of the gun. When the barrel assembly get near the end of its travel, the extractor will snap back down flush with the face of the cylinder ready for fresh cartridges to be loaded into the chambers. Once you've placed fresh cartridges into the chambers, you simply have to rotate the barrel and cylinder assembly back up until the barrel catch re-engages and locks the action closed. The entire process probably takes longer to explain than to accomplish. While this is probably the fastest type of revolver to load and unload, the hinged frame is one of the weakest types (though it's not really an issue with a .22) and also is the most complex and expensive to manufacture.
Most modern revolvers use neither "pull-pin" nor top-break systems and rather use either a gate-loading or swing-out cylinder system. With a gate-loading revolver, a loading gate immediately behind the cylinder (usually on the right hand side of the gun) is rotated open to expose one chamber. Empty cartridges are pushed out of the chambers one at a time with an extractor rod housed underneath the barrel with the cylinder manually indexed by the shooter to line each chamber up with the gate and rod. To reload, fresh cartridges are inserted into each chamber one at a time and the loading gate rotated to the closed position afterward. Gate-loaders are usually single action revolvers patterned after the Colt Single Action Army.
A swing-out cylinder gun has a crane which allows the cylinder to swing out of the frame to one side (usually the left) for loading and unloading. The shooter actuates a cylinder release (the release works slightly differently depending on the make of gun) and swings the cylinder out. Once the cylinder is swung out, the shooter manually pushes an extractor rod which raises an extractor star to push the cartridges/cases out of their chambers to fall away from the gun. Releasing the extractor rod allows the extractor to return flush with the cylinder face so that fresh cartridges can be inserted into the chambers. Once the cylinder has been reloaded, the shooter simply swings it back into the frame until it locks into place to make the gun ready to fire again. Most modern double action revolver including those made by S&W, Ruger, Colt, Taurus, Charter Arms, and Rossi use a swing-out cylinder.