Am I able to turn my Arduino off with code?
Not with just code, but the Arduino could turn itself off with an external electronic power switch.
Yes with a relay for exemple but you can not wake up by program ---> Vcc= 0Volt = microcontroler definivly stoped.
It is possible to put it in sleep mode, see --> Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors