I want to install Windows 7 on my Mac, which is running macOS Sierra.
I can't do this with Boot Camp, since Boot Camp only supports Windows 8 and later.
I need to boot from the USB, which I created, but I can't do it using the usual method of holding down option key while booting the Mac.
I also tried holding down shift key, nothing works, it just starts as usual.
How can I actually boot from USB and are there different keys to press in order to boot from USB or boot in safe mode in macOS Sierra?