So I've done

# mv /storage/emulated/legacy/build.prop /system/build.prop 

on my SM-T311 (Android 4.4.2) and now it won't boot. The only change I've made was adding one line at the end:

net.hostname=Tableta 

I've tried using adb shell to revert the changes, but my PC won't detect the device when connected with USB cable in recovery mode. Although, when I select apply update from ADB windows detects it and it shows up in adb, but I can't do adb shell.

Is there a way to fix my tablet without losing my data, or am I doomed?