I think you have the 15-in model. I have the 13-in. Both mid 2012 are using ivy bridge circuitry means that memory kit can run just fine with your macbook. I still am running this kit for 15 months now with no issues.
Yes it should work just great. After you install, run the Apple hardware test (google to find out how) a couple of times to make sure you aren't getting any errors. That will take the better part of an hour for each run. If you pass OK, you should have no problems. If it doesn't pass, pop the modules back out and switch them in the slots and then repeat the tests. I also highly recommend that you be upgraded to 10.9 Mavericks. I used to get some rare kernel panics with this memory under 10.7 Lion, but after upgrading the OS they have disappeared completely. Then, if you haven't done it already, start shopping for a solid state drive. Since I added both to mine (late 2011 MPB) I couldn't wish for a faster more responsive system.
I just installed 32gb of this memory in my Lenovo W540 (2 sets of 2x8gb) and it works. Pro-tip: when you start up after installing the RAM nothing will seem to happen (no Lenovo logo). Wait up to a minute before giving up. I swapped ram in and out for half an hour before I heard the POST might take a while with 32gb of new RAM. Sure enough, after about 40 seconds the Lenovo logo appeared and everything went well. Another Pro-tip: make sure you have at least Windows 7 Pro. Windows 7 Home will only see 16GB.
The 2013 27" iMac has 4 memory slots, the ram from the factory will fill two of the slots. If you are adding ram you will add the new modules to the open slots. If you are replacing the original ram, remove it and and replace with new modules. Once you have the ram bay open it is pretty obvious.
I'm Fairly certain it is...here is what you do to be positive. Go to the crucial website and download their men scan tool, it will tell you what you have and how much you can expand to. It will also list for you the part number and type of RAM. Then all you have to do is compare to Amazon. I am pretty sure it will work, but I'd hate to be wrong. Again, go to crucial, do the memory scan and double check the part number.
It took about 5 minutes for my IMac to boot up the first time after installing these. I read that if you don't have them installed correctly the computer will not boot up. Did you go to crucial's website to verify that this is the correct memory for your computer?