P: Sorting photos in shared album

Well... I tried again... for the same result, everything is mixed up. Do I have to wait more than 1 minute before refreshing the link?

When you reverse order there is a save that happens in the background.  If you have large amount of photos it's possible to click over to the shared album link before the save has completed and the order will be wrong.  A refresh of the share in that case _should_ show you what you expect.

I used « reverse order » on the display tab and refreshed the browser window for the shared album link, like you said.
It didn’t work for like ten times (and instead displayed photos in a very weird anarchical display), until I disconnected My account from everywhere, reconnected and did the change again...
I hope I won’t have to do this every time I need to sort a shared album view...

It's working as expected for me. Are you clicking on "Reverse Order" on the Display tab, or the Photos tab (it has to be on the Display Tab to be seen that way using the shared album link)? And have you refreshed the browser window for the shared album link?