I have a T420 on Xerox BIOS 1.5.1 I was planning to replace the CPU's , and in doing so I needed to Update the BIOS, I have used a USB and booted into dos and installed the latest BIOS 2.9.0 then realized I should have stepped up the updates. Rolled back the BIOS  thinking I would be back to 1.5.1 but I am now on 2.0.22. I cannot boot from USB device, enter bios menu or boot setup. IDRAC still connects and is on version 1.51.51 (Build 01) I cannot update IDRAC as when I try to upload any files I get below error message.

"OSD35: Lifecycle Controller is not enabled. To enable Lifecycle Controller, reboot the server. During POST, press F2 to enter System Setup. Go to IDRAC Settings -> Lifecycle Controller, select enable, and save the changes. "

I cannot enter bios menu or boot setup