With phones running older versions of Android OS, it was very easy to enable USB debugging mode. But starting from Android 4.2 Jelly Bean, the developer options settings are not available by default. And without accessing developer options, its not possible to enable USB debugging mode on any phone running Android 4.2+.
Apart from enabling USB debugging mode, its sometimes essential to access developer settings on an Android phone to perform some advanced tasks.
Developer settings are hidden probably because 90% of Android users will never need to access developer settings. And if they accidently access the developer setting and make some changes to it, they may brick their Android phone or device.
But its possible to enable developer options again on a Android phone or device running Android 4.2 Jelly Bean or higher. Go to Settings > About Phone and tap ‘Build number’ 7 times. You may see a dialog box after tapping third time, saying that ‘you are only four taps away from being a developer’. But that’s ok, keep tapping.
After tapping it seven times, the developer settings will be available again in your Android phone running Android 4.2 Jelly Bean.