I Need Help With My Quadcopter For My Graduation Project (Gamepad Controller + Esc Callibration Problem)

Hey Guys , I Need Your help and i need you to help me as soon as you know anything , i’m late for my graduation project , it’s Quadcopter using apm 2.6 , i got Emax MT2216 Motors , Simonk 30A ESCs along with Gps & Compass , F450 Frame and finally 14.8v , 5000mah , 25C battery

I Have Flashed The Firmware 3.2.1
I Have Configured The Joystick with throttle , yaw , roll
The output of Escs is Zero , input is the battery voltage 14.8v

i thought i have to callibrate Escs so it can get out voltage to the motors , but i can’t do it as i have to get firmware of 3.3+ , unfortunately APM is not supporting 3.3+ Firmwares due to low memory .

What Should I Do now ?
I Need To Fly It using the gamepad , help me .