So I did the update to 2.37 and tried how to downgrad to V2.35.
The first step was a modified cab based on V2.35 and Infiniivision.cab from 2.37 to change the Windows folder with the ProcessStartupFolder.exe
The 2.37 Firmware has loaded the Firmware Update successfully but it takes a couple of minutes before the scope reboots.
This is the simples way to restore the \windows folder to an older version because ist write protected.
The next Step was to rename the 2.37 to 2.35 in the infiniiVisionLauncher and infiniiVisionCore and replaced these files directly over telnet from usb to the \sercure folder.
after a reboot i tried to load a V2.35 Firmware but this didn't works maybe the timestamp was also checked.
After I replaced the newest files in the \secure\infiniivision folder direcly with the 2.35 Files I was able to load the old v2.35 setup.
So its posible to go back to the V2.35 with the help of telnet access.
Because i did this with try&error i don't have more details at the moment. For the moment I'm happy that my scope is run with V2.35 again an working Usb Startup.
btw It's easy the change the Splash Screen \windows\compileImageForSplashScreen.exe \usb\SplashImage.png \Secure\InfiniiVision\splashImage.bin