MacBook Air - Upgrading from Mac OS X Lion to macOS Sierra
4309
How can I download an older version of OS X/macOS?
98543
How can I download Mac OS X El Capitan without app store?
102094
Delete incompatible ScreenFlow version from MacOS Sierra
122693
How can I upgrade Mac OS without the administrator password?
129143
Error upgrading to High Sierra
63888
Installing OS X not from App Store
72649
How do I transfer a file from a guest account on a MacBook Air?
134561
Is it possible to run Snow Leopard on a LATE 2011 MacBook Pro?
121309
How to downgrade from El Capitan to Snow Leopard?
22323
Install macOS Sierra on VirtualBox?
104017
Upgrading from OS X 10.10 Yosemite Developer Preview
81559
How to install Ubuntu on a Mac and keep OSX?
24542
For equal cost, why would you select the MacBook Air over the MacBook Pro?
131130
App Store only sells latest OS X version? Can't get Lion 10.7 anymore?
90729
Macbook Air + Lion + Windows 7 Boot Camp + shared partition
106321
Finding out if upgrading to a newer macOS version will cause issues?
61672
Using launchd to update MacPorts