Slitherine

I took screenshots of all the pages about how to play. Started the demo and see that the small grey rectangle with the small arrow either pointed left of L shaped arrow refer to the Enter key. By the way, I don't have a gamepad and assume that the game can be played by mouse and keyboard.

I see that there is a exit replay again showing the grey rectangle with an arrow pointing the left. However hitting the Enter key didn't do anything.

Is there a list of hot keys?

How much time does each turn represent?

You may be confusing the Backspace icon (rectangle) with the Enter icon (L-shaped icon). Both are used frequently in the UI.
for list of keys - go to the menu - customize controls. It lists all the commands and keys assigned.