I have a Mid-2011 21.5" iMac, it came with Lion on it. I am currently running Yosemite on it, and I want to download the Lion installer. I tried to boot to Internet Recovery, but it tries to install Yosemite again. Lion is not in my purchases on the App Store, how can I download the Lion (10.7) installer?
iMac, OS X Yosemite (10.10.3), 2.5GHz Core i5 Quad
Assuming you have already applied the relevant update that model should support internet recovery…
https://support.apple.com/en-us/HT202313
That should allow you to boot via the internet & get the original OS.
It's best if you use internet recovery over a wired (ethernet connection) since the OS & the installer will be downloaded, wifi can be unstable or slow in comparison.
Use cmd+alt+r at startup to get into internet recovery mode - it can take a little while, so retry if it fails to work first time, it should be clear that 10.7 will be installed when you boot correctly.
http://osxdaily.com/2014/12/14/reinstall-os-x-mac-internet-recovery/
How do I download OS X Lion on iMac
