If you mean a switch you can flip that disables the car and will not allow it to be started, the answer is no, it is not illegal. It is your car and if you want such a device installed there is no law against it.
Yes
No.
Yes, it is illegal to put no parking stickers on cars without proper authority or permission. Doing so could be considered vandalism or tampering with someone else's property.
yes
Yes, it is generally illegal to put signs on cop cars without proper authorization. This can be considered defacement of public property or impersonation of a police officer, both of which are illegal activities.
Technically no they are not illegal but that really depends on the parts put into the car during the build. But most times the answer is no kit cars are not illegal as long as you go through the processes of getting a vin number form the DMV and getting an emissions test from the police department.
probably because it is a weapons and could either put someone in a comma or crush them or kill them and you pretty much answered your own question because anything that can be used as a weapon (which you said in the question) is illegal.
put nos in cars
It is illegal to do it inhumanely.
The cars were called "Cattle Cars". They were called cattle cars because that's what cattle were put into when they had to travel.
They aren't illegal because we have to put trash in them!!!
No, it is not illegal to put up missing posters in public spaces.