Can i run brushless ESC from any digital pin of arduino {assume arming is done}
Can i connect the brushless ESC to any digital pin and give writemicroseconds() to it? Will this work. because i have connected my 4 ESC's to "~" pins. so i thinks that other will not work.
It should work.

The Servo library doesn't use hardware PWM, so you can connect them to a non "~" (PWM) pin.