sushantvirdi,
Probably not.. you should back up your existing firmware version with s1fwx first before you start mucking around with your 3.5.35 firmware.
Why do you want to upgrade anyway?
Updates for these players rarely exist and you can't use any one elses firmware because they would be incompatible. A firmware upgrade won't make it do magical new things.. not even to play new files or run faster... it will most likely kill it.
The only thing you could do is extract and modify your current firmware to give it a different look.
How to Extract >
http://www.mympxplayer.org/how-to-ex...tool-vt66.html
How to Modify >
http://www.mympxplayer.org/how-to-mo...ool-vt206.html
Oh and if you don't mind.. please share your firmware with us.. it may help restore someones dead player.