If your device hasn't got the hardware for OTG than, no. What ever you flash there will be no OTG function. Alternative - replace your miniUSB port with a new one that supports OTG. After that download the Android Source Code (around 30GB) And make the whole operating system from scratch. You will need to add device specific code for the OTG port to work. I one sentence - It can't be done.
But does this device have the hardware for OTG? Granted, it's tough to give a definitive answer when there are several versions of the Galaxy Tab 3 7.0 (I have the SM-T217S), but I don't know that answer for any of the versions.