Using power adapter

Absolutely.

You can use it, and you can also use larger USB-C power adapters such as those that are primarily designed for Mac computers.

See the following from Charge your iPhone with an iPad or Mac notebook power adapter - Apple Support

You can use Apple USB power adapters for iPad and Mac notebooks to charge iPhone, iPod, Apple Watch, AirPods, and other Apple products.

And also see: Fast charge your iPhone - Apple Support

Yes.

If still in doubt, see the Compatibility section of Buy 20W USB-C Power Adapter - Apple