How ST-Link RESETS the MCU by using Reset pin? How to connect Boot0 pin when it is not used and SWD interface is used?
I've just completed a PCB for a STM32 (STM32F042). The design is minimal:


BOOT0 is connected to ground
NRST is not connected at all
SWDIO and SWDCLK are available for programming and debugging


The ST-Link can reset the MCU using a command via SWD interface. If you want to connect NRST, go as described by Justme.

Update

To clarify question 2: BOOT0 is not needed if you use SWD. It would be needed if you want to upload firmware via UART. So just connect it to ground.