Item 49949 is for 13mm dovetails, however your CZ 455 should have an 11mm dovetail, so item 54231 would be a better option as it is for 11mm dovetails.
Yes, MPN: 54231 or MPN: 54234 should fit depending on what height you are looking for.
The Leupold RM Rimfire No Tap Rings should work on the grooved receiver of that rifle.
The Leupold RM Rimfire No Tap Ring Mount for Scopes w/ 1in Tubes will fit either an 11mm, 13mm, or 3/8 dovetail rail. I would recommend you check to see what specific dovetail rail your rifle uses and then select the corresponding rings.
Leupold does not make this ring set for 30mm riflescopes. You can find a category of 11mm dovetail 30mm scope rings using the link below.
https://www.opticsplanet.com/s/11mm-dovetail?_iv_availability=in-stock&_iv_gridSize=240&_iv_parent-tube-diameter=30-mm
The Leupold RM Rimfire No Tap Ring Mount will not work for picatinny rails. They are designed for dovetail mounts. You can use any set of picatinny mounted scope rings.
Yes, they would be compatible: LU-RR-RING-22RIM-178117
You would need the 3/8" dovetail model: LU-RR-RING-22RIM-178116 LU-RR-RING-22RIM-54289
The 3/8" dovetail model would work with your Ruger American .22
You would want this model: LU-RR-RING-22RIM-178116