Well that is one thing that makes me want to send an enhancement request for, and I am sure many might have already sent that one ! Gee that is sad that we cant do such a 'taken for granted' kind of thing. Anyways I hope that Solidworks does realise the importance of this.
Your SOL on that one Vikas. You can't save back to a previous version. You can save your models out to parasolid and bing them back into a older version but that's it.
Baren-Boym says they came out with a product to do it, but if it's a new function inside the latest version it come over as a imported body. It can do some things but it's not very robust. You might as well save your money and Parasolid out. it's not much different. As you can tell they didn't impress me much at SWWC in Boston this year with it.
That request will never be fullifled anytime soon. You can put the request in, but it's most likly not going to make much difference. I don't think there is a single 3D CAD App. that does save back to a previous revision. If so, then what would be the point of upgrading? On top of that Support would be a nightmare. That would require me to support all versions of SW. It's hard enough to keep up with all areas of two versions (Latest and previous) much less 18 versions of SW (since 1995).
Solid Designer / OneSpace allows you to save to a previous version, but you can't choose which previous version; there is only one choice. Still, it's very handy for people who want to upgrade without worrying about whether their customers or vendors have upgraded as well.