You must remember that when you declare a function, it NEEDS to be applied, for example, in your loop, otherwise it will never be executed (in your code, for example):
void serialEvent() {
while (Serial.available()) {
char inCar = (char)Serial.read();
if (inChar =='\n' | inChar == '\r'){
stringComplete = true;
}
else{
inputString +=inCar;
}
}
}
This function is not called at any time. Soon, you will not get anything to have what you compare.