Which Firmware Should Be Flashed on Sprint 831 C ? Confused !!

Dear All,

Pl. somebody may guide me as to which Firmware shall be the correct one, to Flash with the details of my Handset as below:-

1) Sprint 831 C - M8WHL PVT SHIP - S- OFF,
2) CID - 11111111
3) HBOOT - 3.16.0.0000
4) Radio : 1.00.20.0120.

Further, Since the device came to me in the S-OFF and SuperSU installed on it (Rooted), I managed to install twrp-2.7.0.2-m8.img, for which now I have backed up my complete system, and have nandroid backup for it.

Now, I am curious to install other custom rom as well, my earlier readings / understandings here & after googleling, warns me to do it untill I have the Firm ware updated.

My queries,

1) Should I download the RUU 1.5 GB 1) http://www.pocketables.com/2015/02/s...ia-otaruu.html or form here http://www.htc.com/us/support/htc-one-m8-sprint/news/ and follow the instructions thereby.

2) May I at the liberty to install the Android Revolution HD ROM on HTC One M8 , available here : http://www.droidviews.com/install-an...on-htc-one-m8/

3) Will I loose, my S-OFF, Sim Unlock in doing above mentioned acts.

The snapshot of my device in bootloader mode is attached for your quick guidance.

Pl. help understand the above. Thank you all in advance.

Best Regards
Karan.