Install opencore with macOS Sonoma on unsupported mac on external drive 

I already have an external SSD as the boot disk on a 2017 27" iMac - can I use this to upgrade that to Sonoma using OCLP - _rather_ than erase it and do a clean install?

Hi Dear i Can't install macos sonoma my unsupported mac kindly help me.

Will try for the Fifth time well here goes. downloaded file size 664.2mb, 1.4.3 in your video you are downloading 1.3.0. then it goes throw the steps and goes straight to reboot system and hold down opt key, then computer goes to recovery mode, I am using a late 2013 MacBook pro 15 inch with big sur version 11.7.10 ,512 harsdrive and 16 gb ram and intel iris pro 1536 mb also 128 gb Samsung card 170 write speed is the item used to make boot drive. I can't make a boot drive ? what is the next step?

guys what is the hard disk or the pen drive used for??? does it delete everything in it???? pls help