Clean Safari browsing history, or reset Safari on a regular basis. Repair permissions on your Mac at least once every six months, or if you're having a problem with an application. That is about all the maintenance there is.
This seems to be more of a technical problem. You should take your iMac into the nearest Apple Authorised Service Centre for help.
Yes, you can watch videos on LetMeWatchThis on an iPad, iMac, or Mac book. The service is not available for the iPhone.
No, you can only get that discount on a new iMac not a refurbished iMac.
There is no "iMac Air".
The original iMac was the G3 which came out in (1998). It was followed by the G4 (2002), then the G5 (2004), then the Intel iMac plastic version (2006). The 5th iMac was the aluminum iMac which came out in (August 2007), followed by the iMac Aluminum Unibody (2009). The newest iMac is simply called 2012 iMac and it came out on November 30, 2012.
An iMac is a computer, but a computer is not necessarily an iMac, so they are not the same thing.
The iMac
The original iMac was created in 1998.
No
I do not have a 24" iMac. I have a 20" iMac. Apple no longer sells the 24" iMac. If you will click the Apple logo on the top left of your screen and then click About This Mac then More Info you can find the answer.
The iMac was invented and went on sale in 1998. The iMac as it looks today was introduced in 2006.
There is no apple key on a newer iMac.