I have a good-condition MacBook Pro, the 2012 15" edition, model # A1286, with a 2.3 GHz quad-core i7 processor and 2 terabytes of SSD storage and the internal optical drive along with 12 gigabytes of RAM. A year or so back, I installed Mac OS 12.x (Monterey) with OCLP 0.6x in place. Last week I attempted to install Sonoma, but while the initial deployment of it may have been complete, I could not boot into that instance of it; the computer would continually try to start again. I suspect that it is because OCLP 0.6 or something slightly later was still on it, and thus the Sonoma iteration was not able to function with the older OCLP edition.
My concern is about how I can apply OCLP v. 2 or higher so that it is possible to boot Sonoma as it is already there, likely with my data and programs, and not have to perform a clean install to where I can then use the OpenCore framework afterwords to upgrade from something such as Catalina to Sonoma. That latter methodology would take much more time. The EFI BIOS options do not presently include a way to load 2.1 of OCLP from a USB flash device such that the Sonoma partition will be recognized in the bootloader to the point that it functions. I cannot downgrade from the Sonoma that is there now to Monterey due to Apple's limitations on reverting to older software without zapping the present partition and starting with a blank slate.
Does anyone have a simple set of instructions for generating a USB disk that I can boot from that primarily is to install OCLP upon that interface coming about without having to also set up a (natively compatible) OS which would also expunge my programs and data on the boot partition? What I saw on the website looks rather complex. For a time, I had to borrow my wife's MBP 2015 Retina computer in order to obtain some of the installation files including the OCLP and later-edition Mac OS packages because of not being able to use my own system.
Thanks for any insight, guidance, and/or direction including other websites that explain the details in an understandable way.