BudsGunShop.com - Ruger security 9mm

Not as is. You will need a rail, which is also available. Good luck

No, This optic has an integrated weaver style mount, even if you could find a way to mount this to your security9 (which is unlikely) I wouldn't, this is to big and is not a durable optic it would not be good on a pistol.
A
Couple good budget options for pistol dots
opticsplanet.com/swampfox-kingslayer-1x22-micro-reflex-red-dot-sight.html
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opticsplanet.com/vortex-venom-red-dot-top-load-sight.html

no this requires a top rail

Ethan, if you do not have an Optics Ready Security 9, you will need a mounting plate that replaces the rear sight. You can contact Galloway Precision for details of the needed plate : https://gallowayprecision.com/optic-mount-plate-for-ruger-security-9-pistols