[throwaway3618]

Phones are pretty bad for the group who are scared of breaking something and so don't just try the first thing they guess.

Delete: maybe tap and hold, then three dots or an (i), maybe swipe right/left/either.

Close an image: probably pull down from the top but not always.

Undo: Shake the phone like an etch-a-sketch???

Whereas Outlook Express, for example, looking at screenshots, had a big red X with Delete written underneath it in the toolbar. And your mouse had a physical button dedicated to stuff that's now hidden away behind long-press or swipe or the (i) or whatever.