Chosen Solution
I was trying to transfer my old iPhone backup onto my new iPhone and the upgrade to Sierra came up and stupidly I clicked yes. Well it said there was an issue and to try restarting, I tried 5 times and it wouldn’t work, I tried the repair option then reinstall OS X and it installed but when I went to load it said I couldn’t install as there was a newer version! Help I cannot load my mac and I desperately do not want to lose all my data. Update (08/17/2018) It’s a MacBook Pro 13” I tried safe lad but nothing happened. I don’t have another Mac, unfortunately.
Did you try to load in safe mode? If it doesn’t work you need another mac to create bootable USB and instal it it from there. I think data will not be affected. If nothing else work you will have to install it clean. You shouldn’t perform hard restart, but use terminal “sudo shutdown -r now” command.
