unlock Park

if you mean it won't shift into neutral/drive, you might need a new 12v. not sure what you mean by overheated? did the coolant leak out/fan stopped working/thermostat fail? you could try disconnecting and reconnecting the negative 12v battery cable.

 

temporarily disconnecting the 12v negative for a minute resets the computers. this may work for you, but i'm not sure.

 

Unfortunately the shift lock actuator, or parking pawl motor, is difficult to access, as it is also a theft deterrent. There is a way to make the actuator to run if the car is not doing so, as a result of error conditions, in the post from imwoody36:
How do you put the Prius in neutral to push or tow it? | Page 2 | PriusChat

I haven't tried this, but this is the best that anyone has mentioned. There are other posts here, that mention using a wheel dolly under the front tires. Do a search for "shift lock actuator" for more ideas on how to move a dead Prius.

It is necessary to put the car on a lift so that one can get under the transmission if, as a last resort, one has to unbolt the parking pawl motor. Big hassle.

 

Try putting the Prius in ignition on mode. That requires two pushes of the power button WITHOUT holding your foot on the brake. You should be able to shift to N and get the car off the street as long as the 12 volt is working for you and not discharged. The 12 volt is not a real strong battery, so it won't last a long time in this condition. To turn off simply push the power button one more time and the Prius should power down.

Don't forget to hold down the brake pedal when attempting to shift to N from P.

 

If the car goes into N as Ron describes, then you can pull the PCON relay (under the hood) out before turning the car off again. That will keep the parking pawl motor from operating, as it usually does on shut down. Then you can tow the car in the off state, and no worries about the 12V going flat. The foot operated parking brake will still work.