Thanks John. I have made the change in the boards.txt, saved the file, restarted respberry, but the issue remains the same. When I use 9600 baud in sketch, the serial monitor only works if I set it to 1200 baud, otherwise, the serial monitor will show garbled content. I am now guessing that probably I need to do something to apply the changes. I double check the boards.txt and I confirm that it does have the new values, but still nothing in serial monitor changed.
Just realized the images of the configs that I attached below is for a different board. I did the change for the Arduino Uno board as well, nothing changed at all. Same issue.
Below are the old values in the boards.txt. I have already updated them with the values you suggested.
.fcpu = 12000000L