Kindly provide below information for the part# NRF52840-DK (OC: 2842321).

[Hanamantappa]

If we input 5V DC supply to Vin 3-5V P20, the Bluetooth programming failed at start.

But if we input 3.3V DC supply to P21, the Bluetooth programming passed.

Is this Vin 3-5V at P20 able to use to power on the MCU and Nordic board ?

The only USB for programming and debugging is via J2.

[ketiljo]

If we input 5V DC supply to Vin 3-5V P20, the Bluetooth programming failed at start.

This should work. Check the power supply

 

But if we input 3.3V DC supply to P21, the Bluetooth programming passed.

 Yes, correct

 

Is this Vin 3-5V at P20 able to use to power on the MCU and Nordic board ?

 See the HW description for the DK : https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/nrf52840_DK/5V_power_sources.html

All sources are connected the same place and supplies the boost regulator.

 

The only USB for programming and debugging is via J2.

 Yes, only J2 is connected to the debugger MCU.