I bought an ex demo unit of a Samsung Galaxy Tab A 9.7" (SM-T550X) and struggled at first trying to get it out of retail mode. I tried using the easy to find method using the two passwords, but it would just reboot and be back to normal.

So I read about using Odin to flash the tablet with firmware (I used Odin v3.11.1 and firmware 6.0.1 T550XXU1BPE1_T550BTU1BPE2_HOME.tar.md5) which completed and removed the retail mode.

However, the apps are still on there and I cannot remove them, and I cannot reset to factory settings. In the general settings the option to factory reset is greyed out, and using the POWER / VOLUME UP / HOME menu to factory reset brings up a quick message at the bottom that "MDM does not allow factoryReset" and it just reboots.

I'm very new to Android so I don't know if I am now stuck with a large proportion of space eaten up by what I can only assume is a partition of some sort that doesn't get removed by Odin?