In general, no. However, if you are waving them down for no real reason, and do so repeatedly, you might have some trouble from them. If this is truly an issue, consult an attorney in your area for advice specific to your situation.
In the UK it certainly is.
yes it is illegal, you most likely will be fined for it if you do it in front of a cop.
It is an "assault" and therefore, unlawful.
Not if he has cause to do so.
Yes, it is illegal to make your car look like a cop car as it can be considered impersonating a police officer, which is a crime.
when a cop can hear it from the inside of his car
haha its illegal to lie to a cop period.
Mabye maybe not
It depends on the circumstances.
It is slang for a criminal or illegal act such as burglary or robbery.
Of course, unless the picture is of an illegal nature.
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.