@Leung: Inside a person's face group, if you select picture, and you hit the silhouette with an X, it is just removed from that person's database. Using the trash can elsewhere will result in deletion.
> I re-tag the person and how can I change the icon
change the icon: Not yet possible, but will be done shortly.
re-tag: it goes back to the untagged pictures, and you will find it there at the bottom. However we are presently limiting that screen to 100 entries. We will change that to 200, or 300. Originally, it was unlimited, but created UX issues.
> How can I tag a face that is not recognised as a face by the app?
Not implemented yet. But as we overhaul facial recognition, will be.