So it is locked for other pc specs?
And if you change the harddrive then you will need to install the os with a disk or usb. And it takes space on the harddrive, soo seems logic to me that it is on the harddrive.
And yes boot up with ps4 os.
Again, the PS4 is coded against VERY specific HW, down in some cases to hardcoded assumptions on bus timings. No matter what you do, your PS4 OS isn't running as is on a PC, no matter what hardware you have inside it. At minimum, you'd need to emulate the entire PS4 OS/HW architecture.