HEREBinaural, there are so many versions of 3.5.35 that it is impossible to say which firmware would safely upgrade your firmware.
The only sure way to ungrade your theme without killing your player is to extract the firmware from your player then theme it yourself.
Here are the resources you need to do this.
S1fwx to extract and repair your firmware.
DOWNLOAD
A guide to using s1fwx
HERE
s1res to change the images in your firmware
DOWNLOAD
A guide on using s1res
HERE
You can find many themes and images that members have uploaded
HERE