I got some idea about putting the arduino in boot loader mode by double pressing the reset button. To return back to normal mode i need to press only once. But, This works when the current state of my Arduino is not in bootloader mode.
But when i run any model (in external mode in simulink) in simulink, It gets stuck in boot loader mode, and gives me error, then it does not return back to normal mode. I don't know how to solve this arduino MKR1010 board problem.
and, still i am waiting for a better & concrete solution.