OS X downgrade problem (stop symbol appears)

[iMore Question]

Hi guys,

I purchased a refurbish mac book pro a few weeks ago, I think they are the early 2015 model with El Capitian intalled in them. I am a sound editor and is using software that is not really compatible with both El Capitian and Yosemite. So I decided to downgrade my OSX. I made two bootable USB drive, watching the online tutorial, one usb has the mountain lion in them and one is maverick. I restart my mac and press option key to go to the booting drive page and click my usb drive with OSX in them and tried to boot them, but here comes the problem, both usb drive when I click them, it went in to a white screen with a stop symbol in them. I went online and did a ton of research on this matter and I can't seems to find any solution.. PLEASE HELP! Thanks in advance...(All the tutorial online that tried the same thing as I am seems all had successfully downgraded)

(side note: I went in to the recovery mode and is able to downgrade my OSX to Yosemite, but as I said before, my software is also not compatible with Yosemite...)

Thanks,
William

 

[njlx2016]

OSX Recovery will install the version of Mac OS that the computer originally shipped with which in your case is Yosemite.

If the computer shipped with Yosemite (10.10) then you can't downgrade any lower than 10.10. If the computer shipped with El Capitan (10.11) then you can't downgrade any lower than 10.11. Macs that shipped with Sierra (10.12) can't downgrade any lower than 10.12.

You're getting an error message because you're trying to run a version of Mac OS that is incompatible with the hardware you're trying to install it on.