Answer to : How to access terminal in Sierra's recovery mode?

I had the same problem. (the previous conversation thread has been closed)

Solution : The standard shortcut works (⌘ ＋ R), but you must NOT use your mac in <<clamshell>> style. use its keyboard. And Utilities on Main menu bar before you select and go to Disk Utility. ( I mean you don't need to open it up). Just make sure Recovery Mode load it up completely.