Updated to Tahoe by mistake

ooking for help please. I had an earlier post but now I’m running into resetting issues.

I have a 2015 MacBook Pro. Specs really don’t matter. And I don’t have them readily available. Worked perfectly for what I needed. I used an open core legacy tutorial to install a different/newer OS. Everything worked fine. Then I accidentally updated to Tahoe. Now my Mac boots up to a login screen where my password doesn’t work. From what I’ve read there’s nothing to do but reset the Mac. Which I’m fine with. I created a bootable usb. But I can’t seem to load it up.

Hold down option when powering on and all I get is the attached picture. And everything I click brings me back to the login screen.

Please any help is appreciated. All I want to do is reformat/reset and start fresh.