Verifying device integrity. Galaxy Tab S2 9.7" I wanted to root my Galaxy Tab S2 9.7" LTE (SM-T815Y) and I have spent the better part of my night doing the following. (I have never rooted anything before)


Got a img of autoroot from some site and flashed it via ODIN.
ODIN application showed success, but the tablet refused to boot after that with red text at the top of the screen at boot logo RECOVERY NOT SEANDROID ENFORCING
Download mode shows KNOX flag has been set to 1 and the warranty is void.
After a few hours of trying things, I managed to install TWRP 3.0
While the error stayed, I could now boot to TWRP
Scoured the internet for stock or samsung images that can work.
Found the cyanogenmod for my device (Nighty 2016-08-31 05:00:43 version as there nothing on the release channel)
Attempted flashing it using TWRP.
It noted that the image fully supports SE ANDROID (or SELinux, or device supports one of those.. Can't remember, the text scrolled so fast)
Then it failed to install.
I rebooted the device and it looks fine and the SE ANDROID error is gone.
Seems like everything is where I left them. Data was not gone, even my homescreen shortcuts are there.
(Took a full backup using TWRP. Coz... lessons learned.)
Ran a few apps to check root status, and they all show the device isn't rooted.




So, since I barely understand what I did, my question is, 


Can I go back to the factory recovery? (remove TWRP and put back samsung one. Also, where to look to find the factory recovery? Samsung doesn't seem to publish it)
Is the device still using the Samsung OS image? Or is it a combination of the factory image + whatever my CM flash attempt did?
I Assume SEANDROID issue is part of KNOX? If so, should I disable KNOX (how?) before attempting to root again?
Custom recoveries and ROMs don't enforce SEAndroid, so the error pops out. Ignore it.
Get stock Samsung images from SamMobile. This is also the surefire way to return to factory recovery (along with everything else).
Please get a screenshot (camera capture) of the failed CM installation, so that we can diagnose what's the issue.
Assuming the flashing process failed at its start, it doesn't even wipe anything, so it's stock Samsung system + TWRP, nothing more.