Hi @Manoj
For all devices :
in Requirements
3. Enable USB debugging on your device.
may link to detailed steps for making visible the developers options
For Samsung devices
Many time it’s written :
Boot into download mode:
With the device powered off, hold Volume Down + Home + Power.
Boot into recovery mode:
With the device powered off, hold Volume Up + Home + Power.
But nowhere mention how to power off the device when you are stuck in the download mode :
To power off the device, hold Volume Down + Power.