ImageView: After using pinch & pan would like to restore image to original size & position with a tap. Have tried but failed. Anybody have a solution?

Double-tap to zoom in, then back out is considered a 'standard gesture' for images. That means the dev is obligated to use them as-is, and not casually appropriate another standard gesture that users are already trained to expect to behave differently.

Even if you make single work, you risk rejection during review.

See the HIGs: https://developer.apple.com/design/human-interface-guidelines/ios/user-interaction/gestures/