Both FM 13 and FM 12 use the same format, fmp12. So you can take a FM 13 hosted file and download it and then upload it to a FM 12 server and it will host just fine.
Moving backwards always has issues such as functions in 13 server that will not work on 12 such as the Perform On Server script step.
Other issues are that FileMaker apparently changed some under the hood CSS work between 12 and 13 and every once in a while, making changes with 12 will cause a layout to behave unexpectedly. It is fairly unusual, but just be aware of that possibility and the need to test it.
Thank you so much for responding. It is very helpful.
Grocery Outlet Inc
5650 Hollis Street
Emeryville, CA 94608
Thanks Taylor. I uploaded my FM13 file to my hosted FM12 database. Non of the new bells and whistles like pop over are available in the FM13 file. Why is that?
Those features aren't supported in FMServer 12. You have to have FMServer 13 if you want to use the new stuff.