If Rufus made a proper job of combining itself with the ISO and made a bootable drive, check in the BIOS to see if USB Legacy Support is an option then make sure it's enabled. Without that, there's no power to the ports at boottime until the Operating System cuts in.
In Boot Options, put the USB drive at the top of the list. When there isn't a device plugged in it doesn't matter if it stays there.
ONLY "preparing automatic repair"/"diagnosing nothing else all came after Reinstall windows 8.1 by USB no DVD i have usb did NOT boot any thing please help i am on weel---------- on O-D-S-P
its the only one to help me in the life i hate my wheelchair but its my love too
If you want to reinstall, download 8.1 from Microsoft's website then search for and download a utility named Rufus. Install Rufus then follow the instructions it gives you to make a bootable drive out of a SanDisk or other type of memory stick. It would need to be at least 16GB.
Tell Rufus where to find Windows 8.1 in your downloads folder and complete the process. The stick will then boot up the machine and install 8.1 on to your hard drive. You will, of course, need to rescue any files and folders you want to keep and put them in a safe external disk.
EDIT: OK I re-read the first post and you've truied all that but you also said BIOS was unobtainable, then that Windows was trying to repair itself. Is it that messed up that it starts one minute but not the next?