I upgraded to Yosemite on my 2011-12 iMac, from system 10.6.8. It worked to a point, but with major problems with the mail - crashing and not working, basically.My Mac tech said it "should work"...but we tried reinstalling 3 times to the same result. Given Mavericks is no longer available, does anybody have a suggestion other than a clean install of Yosemite? Or is that the only option?
Yosemite mail is horrible, if you have a large inbox it just kills an older machine. I have a 3ghz mini with 16gb of ram and it STILL crawls. I am on day 3 of it saying "incoming messages" and slowly the count grows larger and larger. Two apps is all I ask for, Safari and Mail, really people FIX IT.
On my 2009 27" imac I had to restore from time machine back to mavericks. If you start a restore it will show you what os version was backed up. Just know it erases your drive so save all of your newer files elsewhere.