What if I detach AVR micro controller from the Arduino Board after uploading program?
The AVR µC got a flash memory that can store the code loaded in. That mean you can load the code with the arduino board, detach the avr and put it on another circuit. If the µC is powered well, it will behave just like the arduino. 

Don't forget to set the /reset pin to high, if you do, the µC will be stuck to the 1st line of code ;)