Q: Can we install safari 7 in lower OS versions like Mountain lion or Lion?

If Apple provides a version 7 for ML and/or Lion, sure. But I believe those two OS's are still at version 6 and only version 7 can only be installed on OS X Mavericks.

What's in version 7 that you feel you need in OS X ML/Lion?

Gotcha. No, not to my knowledge.

You need to remember that Safari is not a standalone app to begin with. There are two components to Safari. Webkit, the browser engine that Safari (as well as Mail, iTunes, the App Store, etc.) depends on to do its thing, is a deep down framework component of OS X itself and can be OS version dependent itself. Safari, the app itself, relies on Webkit totally. Tinkerers have installed different versions of Webkit and the Safari app to mixed results. For compatibility testing your best option is to have an actual Mavericks installation and Safari 7 running. It's the only way to truly know if your web coding works properly.

There's no suitable Safari 7 for Lion & ML. If you need to test, create a small partition for Mavericks.

Let me know if any third party can provide Safari 7 installable for MAC Mavericks

Not sure  I understand your question. If you install Mavericks, Safari will automatically be included. You do not download it separately and updates will be automatically provided by Software Update. You should not ever download any Mac OS apps or components from a third party site.

You can download separately, but would not advise... makes it so Safari 7 does not work at all as it is intended for Maverick. I have OS X 10.7.5 and was alerted when I went to MSN.com that my browser was out of date.  I searched for safari updates and was able to download Safari 7... which then left me stuck.  It would not launch... saying that there is an incompatibility issue... that Safari 7 needs an update to Maverick.  When I tried to do that, I was blocked as my MAC can not take the new OS.

Yes you (we) can!

Just download the latest Mavericks update 10.9.5, open the .pkg with pacifist and extract Safari 7 to Desktop. Right-Klick it and choose "Show Package Contents". Now open info.plist with TextEdit, search for "LSMinimumSystemVersion" and replace "10.9" with "10.8.5". Keep in mind that extensions will not be loaded because of the passwd from Keychain's "Safari Extensions List" isn't the one needed.

Cheers!

Great, so my ML is still worth to use! I need on of my Macs with 10.8.5 for an older App running my Work Time Tracking Software

I recognosed one problem.

This modified Safari doesn'r recognised the entries of my Keychain. All pages with an password ask my login Password :-(

Only Idea how to fix this?

Gérard

Interesting. I've tried the same method for Safari 9.1 too, but didn't work Is there a specific version of Safari up to which this procedure can be applied?
Thanks