There is no way to do so, since Kentucky has no registration requirements. You can transfer ownership by going to a Federally Licensed Dealer and filling out all the required paperwork and the receiving party receiving a "go" from the InstaCheck system. That way the gun will not trace back to you as ownership then resides in the transferee.
Email them, but usually you can't unregister
The answer is "unregister"
Unregister, or maybe disregister
yes
how will be unregistered from sms7.in
You can't.
The answer depends on what you mean. In most of the U.S. there is no such thing as registration. In the few states that do require it, it must stay registered in the name of the person that owns it always. If you live in one of those states and move to a state that does not require reqistration, there is no way to unregister the gun, because the states that don't require it can't do anything about the registration in another state.
You will have to get a lawyer
you cant
Kentucky does not have registration of firearms. You CAN pawn a firearm that you own. The pawnbroker is required to make a record of your identification, and description of the gun, including serial number. If that gun is reported as stolen, you would have some explaining to do.
a couple of hundred meters
Your local police can tell you.