Yes, this Boyds Hardwood Gunstocks At-One Thumbhole Stock is compatible with the CZ 457 American with a detachable magazine. Barrel dimensions: Point A = 7/8" Point B = 7/8". Center to center action screws: 5 1/2". You will need take down screws from the factory stock, a lug will be provided with the stock. If you are switching from a synthetic stock with no removable floorplate you will need to purchase an aftermarket trigger guard floorplate assembly to complete your build.
No. However, Boyds Hardwood Gunstocks does make this stock for the Varmint model CZ 457. Unfortunately, we do not currently carry those specific model stocks.