To be able to use an external microphone with the iPhone 12, you will need to use a Lightning to 3.5mm jack adapter, as the iPhone 12 does not have an external microphone jack input. Once the adapter is connected, you can connect the external microphone to your device and use it to record high-quality audio.

As for the flash, the iPhone 12 comes with a high-quality built-in flash that can be used to take photos in low-light conditions. However, if you want a more powerful or customizable flash, you can use an external LED light that is compatible with the iPhone 12. These LED lights can be easily mounted on your phone or tripod, and they offer greater flexibility in adjusting the lighting to take high-quality photos.