The Android "back" button

I am an Apple iPhone user. I have never owned an Android of any type so I am used to the button I have to tap on the screen to go back a screen instead of the physical "back button" that Android has. An iPhone developer has to code the back button in for the user to operate the game but an Android developer does not necessarily have to code a back button and can just rely on the physical button on the phone. My question is if it is okay for me not to code a button for my Android app and just let the user use the hardware back button on their phone? If there is no back button to tap, will an Android user instinctively know to hit the physical back button to jump back a screen? I don't really know this answer since I have never owned an Android and always rely on the iPhone coded in buttons. The picture below is me coding in the back button instead of relying on the physical button on the phone. I am wanting to back out the back button from my code.