Yes, you can use P0.00 and P0.01 as normal GPIOs. But these pins are also used for the external 32.768 kHz crystal, so if you are using the nRF52-DK or using the external crystal in your design, you can’t use them as normal GPIOs without disconnecting the external crystal.
If you are using the nRF52-DK, and don’t have any other available GPIOs and really need P0.00 and P0.01 as GPIOS, you can cut the shorting track on SB1 and SB2, and solder SB3 and SB4 to disconnect the external crystal.
