What do you mean st link ? This jtag is not st link. It's IDAP-Link designed specifically to flash nRF5x series. We use them for both development and production flashing
Yes, to processor is ARM Cortex-M0. That is the core processor. The Flash memory however is what you need to program not the core processor. Of course you can use any jtag as long you have the driver for the target core and flash memory inside the target.
