Help me discover if my 2nd hand note 4 has ever been rooted/flashed

I have minimal experience when dealing with rooted/flashed phones and its been a few years since ive dealt with it.

I purchased a second-hand note 4 from eBay which was listed as being 'new other'......basically, it was an opened package but never used from a seller who sells a lot of this type of thing. Got the phone great and set it up.

First, thing that bothered me is that when I came to do a factory restore and was presented with a black screen with various options coloured red and blue ( i cant post images because im a new user)

The screen says:

Android system recovery <3e>
LMY47X.N910T3UVU1DOG1

volume up/down to move highlight;
power button to select.

reboot system now
apply update from ADB
apply update from external storage
apply update from cache
wipe data/factory reset
wipe cache partition
reboot to bootloader
power down
view recovery logs

dm-verity verification failed......

I also powered down the device and entered download mode
the knox warranty void: 0x1 (3)

Under about device i have

android version 5.1.1

baseband version N910FXXU1DOG1

kernal version
3.10.40-5260683
dpi@SWHD4401 #1
thu jul 30 14.07.48 KST 2015

Build number
LMY47X.N910FXXU1DOG1

Security software version
MDF V2.0 RELEASE 1
VPN V1.4 RELEASE 5.2

Also under device status it says OFFICIAL........not modified which I wasnt expecting.

If i got to KNOX active protection it is switched OFF and it wont let me turn it on.

I dunno.........I seem to think at some point this phone has been rooted or flashed


Obviously if this has been rooted/flashed then ill be contacting the seller as it wasnt advertised this way and i dont mind keeping the phone if i can get a partial refund.

So do I have a shot at a partial refund if this phone has been rooted/flashed?

Can I still reflash/re-root if I want?

Thanks

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