Smackflad:
I have tried to do the third and failed because when I turn off the switch the relay won't turn the light on. But the opposite works.
I have also tried to do the second and make the switch to send signal to the arduino so it can control the relay but when the switch is off it sends random 1s and 0. When the switch is on is correct and send only 0. If I fix this the project will be solved.
Sounds like a floating pin. Enable the internal pull-up (set pinMode to INPUT_PULLUP) or add an external pull-up resistor.