Need to recover android system for soft bricked Onda v919 4G
I am not familiar with the system/etc/parameters directory. What you have done is altered the system configurations that appear to be used at boot. You would have needed to install a custom recovery when you rooted your device. Fastboot is ,in essence ,the equivalent of that recovery except it is included in the Android SDK(Software Development Kit).Most custom recoveries also include a fastboot option.  You will have to scour the web to find a version of the stock firmware for your tablet. 

For future reference, be very careful when accessing or dealing with the system directory and especially the /etc directory as it contains configuration files for your Android system.