On the library. The library is a Safari web browser window. [Backspace] in Safari is "Back" so it goes back to no page at all. To get the library back use [Command]+[right arrow] to go "Forward" tot he library. We've tried to make Safari just not do that but, no. Windows machines use a Chrome browser window and it obeys the "Don't navigate away from this page" settings.

For the screen recording, that's for the color picker. For the color picker to work it has to access the screen. I don't know why it keeps asking. Once set your Mac is supposed to remember the setting.