How to get the buzzer work after storing Serial.read()?

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2 
char inData[] = "";

An array of chars that contains one element. How is THAT useful?

String inParse[] = "";

An array of String objects containing one element. How is THAT useful?

    char inChar = Serial.read();  //if comment this 1
    inData[index] = inChar;        // and this 2
    index++;

You REALLY need to make sure that you don't store data beyond the end of your one element array.

    if (Serial.read() == 13) { // \r cannot be detected if I were to use buzzer. Use 13

Read another character, that may not have arrived. If it is something, do something. Otherwise, throw the value away. How is THAT useful?

At this point, I gave up. None of the rest of the code makes sense, because you have made fundamental errors before this.