I started with the op-amps. I put it in the non-inverting mode,  I measured the voltage at the Arduino compatible I/O header J2.  I could measure only digital voltage VDD = 3.42 volt. When the noninverting input is connected to VSS the output becomes zero. There is no in-between value. Though  I  selected 3 analog pins. I took one example for op-amp. For this also no analog output. If the pins can give only digital output then why analog pins are listed in components? Next I'll try the ADC input pins and check whether I can get an analog value. Following gives the screen-shot of the circuit.