While you are on the site, in your browser find and click "Add to Home Screen" A CGN beaver app icon will then be created to your phone that is directly link to the site.
Note: This feature may not be available in some browsers.
Impossible to answer - there are just too many variables. All things being equal (and they never are), the two designs should be capable of similar accuracy, usually 1-2 MOA for the best guns, with the best ammo with the best shooter.