The sound suppression of the NRS-2 is by way of the special cartridge, which is used in certain handguns as well. The knife's barrel is just a short barrel. It is awkward to fire and meant for sentry or dog elimination. But effective range is about 7 yards. I have fired one a few times years ago and don't know of any in private hands.
Tracked vehicles are street legal in certain states. Texas, Kentucky, Kansas for example. But as stated, these are considerably oversized so these would not.