[highlight][purple]NO, NO and thrice times NO![/purple][/highlight]
This question is asked every few weeks and as stated above the answer is a resounding NO!
The best way to make a file openable in an older version is to save it as a Parasolid (.x_t or .x_b) file. This will create a "dumb" file, but if you have the Feature Recognition module you will be able to use it to rebuild a Feature Tree.
Here's just a few of the many threads about "backwards compatibility";