The one you can afford that meets your mission requirements. At least on of the major makers will have a model that can fill your needs
"Tactical Rifles" are intended for offensive or defensive use at close range, with fairly instant results. Under pressure, tactical rifles are typically used when all other precautions have failed and lives are in danger.
Cheytac inetvention hands down
The best place to get information on the Remington 870 tactical rifle is on the Remington website. Another place to check is firearm forum where any questions or information can be shared through peers.
There is no such thing. A rifle is a tool, there are many different kinds of rifles for many different kinds of applications. A varmint rifle is a bad tactical carbine. A benchrest rifle is a terrible brush hunting gun. Just as there is no best overall hammer or best overall vehicle, there is no best overall rifle. Use the right tool for the job.
18 in the US
You would have to define "tactical rifle". In most of the US, no license is required for rifles or shotguns. Full auto firearms must be registered with the US BATFE.
AimPoint, EOTech, Trijicon ACOG.
no immediate threat is present
No, it is a spring rifle
Does not exist.
360 fps
LaRue Tactical specializes in the manufacturing of custom parts for automatic and semi-automatic rifles. They have a wide range of product such as scopes and rifle mounts.