1. My aurora r12 came with a 1tb hard drive and 2. I just prefer windows 10 over 11, just my preference. 3. And can you explain what secureboot is and also this cloning thing. I seen the term cloning being used a lot and not too sure what it means.  4. If switching the boot device isn't possible then, is there any solution to the error code I was getting about issues with the \BCD file?  The error code I kept getting was 0xc0000098 and most guides weren't too helpful with it. I've been trying to avoid spending money on a USB to fix this but if that's the only solution here I can do that. 1. Really? Not sure how that happened... but it's a bit of a travesty to boot and run an Aurora-R12 on a slow spinning HDD. 2.5inch-SATA-HDD is a little faster. A M.2-NVMe-SSD (which your machine supports) is light-years faster. The whole machine will run faster/better. 2. Not sure what to tell you. Support for Windows-10 ends soon. Windows-11 is the current version for over a year now. If you have a particular issue, we can address it. To me, it's the same, yet better. With your Windows-11 Dell-OEM license, you might have down-grade rights ...not sure. I'm not even sure it ever shipped with Windows-10, so complete driver support might be limited. 3. Probably better if you Google that stuff. Maybe watch some YouTube videos. I use Macrium-Reflect for Drive-Imaging and Cloning. 4. Sounds like you are fighting against the Windows Boot Manager. I think your problem is created by the fact that you are trying to do something that is not supported by Microsoft or Dell.  
So today I had installed my old SSD into my desktop because my HDD that came with my desktop had Windows 11. I wanted to use Windows 10 on the SSD since it's more my style plus just have the SSD for quicker loading times on everything. After installing it, I can't figure out how to switch it to my boot device in BIOS? When I try to boot with my HDD it gives me an error about the BCD file and takes me into recovery settings. I tried unplugging the HDD and booting with only the SSD and it won't even go to Boot Manager. I don't know if my pc doesn't allow me to switch boot drives and I also don't know how to fix my other HDD. I've tried countless solutions to no avail. Is there any way I could get my pc to detect the SSD as a bootable device via recovery settings or bios? Or a way to fix the HDD and get that to boot while also having the SSD in still? Any help would be great!
Aurora R12, can't boot after installing SSD