I am currently using Arduino 1.6.12 and tried uploading the program in a circuit. This circuit with the same program has been tested earlier with Arduino 1.6.9 but now when I uploaded the program using 1.6.12 version my circuit behaves very uncertainly, why is this happening please help!
Please post the whole sketch (not just snippets) and a schematic (not fritzing, we hate fritzing here), and describe what has changed in the behavior.
I have seen no issues involving the behavior of the uploaded code (some in moving from 1.6.9 to 1.6.12 - but there are very significant changes under the hood in the form of Link Time Optimization, which reduces the compiled size of the sketch by 10~20% in most cases.