Change Apple Iphone Passcode from 6 to 4 Digits or Alphanumeric

 

From your Iphone 

Go to"Settings" > "Face ID & Passcode"

Type your current Passcode > Scroll down to "Change Passcode"

Type your current Passcode > "Passcode Options"

Select your option: "4-Digit Number Code" or  "

Type your new passcode