Hardware reset in nrf52840

I am looking for help in doing a hardware reset. How can this be done? Do I need to make P0.21 active low so that P0.18 is enabled to be in RESET mode? This is for hardware reset of SoC whatever be the case using PB SW and a pull up resister. I am planning to use reference circuit 4 of nrf52840.

Will I need to enable P0.18 by making this pin active low in addition P0.21 being active low?

For programing SoC, can I just connect connect P0.18/RESET to programmer connector? 

Thanks

Vishwanath