A bit confused about right disk + recovery

I want o install Sonoma via OCLP on a late 2013 iMac to internal SSD. I have no data to save, so started with clean install of Success' href='/2020/12/install-macos-catalina-on-supported-pc.html'>Catalina first.

From there, following the OCLP instructions I first create Sonoma installer on an external USB SSD. But when it comes to installing OpenCore next, which drive am I supposed to choose? When I proceed with the external drive -> boot to EFI boot/install Sonoma, then install to internal SSD, it then boots ok, but confusingly OpenCore then shows a message saying that I'm booting from external drive (I'm not) and would I like to install to internal drive?

Also I have a question about recovery partition. I was hoping that after I install OCLP, it would keep the original Success' href='/2020/12/install-macos-catalina-on-supported-pc.html'>Catalina recovery in case I (or someone I pass the iMac to) want to easily go back to Catalinait, but it seems not to be there - pressing Cmd+R on boot only shows the crossed circle sign, the proceeds to internet recovery (I can see OCLP recovery by pressing space on boot menu though).

Author: @pwalkow