Question: Run 2 different OSX on 2 partitions of the same HD
Hi there. I purchased an iMac 27" running Mountain Lion (OS 1O.8.5).
In order to keep using older software, I need to keep this OS version.
However, I partitioned my HD to be able to run the latest OS on the new HD partition.
I understand that I cannot install directly the latest OS Sierra on my new partition but have to go through El Capitan first. Is that correct? I tried to get it from the Apple store but it says my computer doesn't meet the requirements.
Do I need to purchase Mountain Lion from the Apple store, install it on the new partition, then upgrade to El Capitan and finally to Sierra?
The desired outcome is to be able to boot from either one of the 2 partitions and use one OS or the other.
What is the best way to proceed?
iMac (27-inch, Late 2012), OS X Mountain Lion (10.8.5)