Sierra stuck at boot screen, upgrading to mojove will create new bootup files?
I also suggest better to upgrade and mostly it might fix your issue. Kindly use the following keyboard combination as per your requirements. 

Basically, as per Apple Guidance:

Command (⌘)-R Install the latest macOS that was installed on your Mac.

Option-⌘-R Upgrade to the latest macOS that is compatible with your Mac.

Shift-Option-⌘-R Install the macOS that came with your Mac, or the closest version still available.