The Mark iii and Mark iv have a mag release on the handle of the weapon just below the trigger. This feature was not available before the Mark iii. Mark i,ii, have a bottom of the handle mag release and are not designed to release with the Mag release on the Mark iii, and Mark iv. Very different manufacturing on the magazine of the Mark iii and Mark iv. The earlier Mark i, ii have a bottom of the handle release. The Mark iii, iv must have a release notch that the Mark iv release button engages.
No, unfortunately these magazines will not fit that pistol.
As long as its a mark series and not a 22/45 series that should work.
The listing title is likely from a previous model that was listed on this page. Currently MPN: 90645 are the "E-nickel" silver color magazines.
These magazines are meant specifically for the standard Mk III and Mk IV rimfire pistols. These magazines will not fit any of the 22/45 Mark pistols. The two pack of 22/45 magazines can be found here: https://www.opticsplanet.com/ruger-90648-ruger-mark-iv-22-long-rifle-10-rd-black-finish-90646.html. Please be aware that these are meant specifically for the Mk IV and you would need different magazines for the Mk III.
While not pictured (they are removable), they do come with.
Yes, it is a two pack.