Developer Edition confusion topic

Hello guys,

1. I bought AT&T unlocked M7 -> I HTC-Unlocked it, then Rooted it, and then did S-OFF -> Then I Installed GPE (Google Play Edition 5.0.1) -> Everything worked great.
2. Then I got bored of GPE (In just 1 day) -> Installed "Combined, NoWipe ZIP" (7.15.401.1 ) -> and Installed "RUU_M7_UL_K443_SENSE60_MR_BrightstarUS_WWE_6.07.1 540.2_Radio_4T.28.3218.04_10.33E.1718.01L_release_ 404528_signed_2.exe" from HTC site -> Phone is working fine with my T-Mobile USA sim.

But when I was setting it up, I saw a list of unknown carriers. Luckily T-Mobile was there, which I selected. So my question is did I flash European or some other firmware?

My M7's Current Info:
1. Bootloader Unlocked
2. S-OFF
3. CID: 11111111
4. MID: PN0712000

FIY: I just switched to Android from IOS. Just 2 days ago I learned (A very hard way) how to do all this stuff (Thanks to xda-developers and some youtube tutorials).

[Q] S-off hboot 1.56 confusion topic

I am currently using ViperRom 7.02 with ElementalX kernel.
I am S-on. hboot 1.56
Currently i was trying to S-off with this combination using rumrunner method , but it goes to pouring 8 times and in the end it tells me to wait 30 seconds before turning the device back on (even though it never shuts down) and running rumrunner again. I have done this several times to no avail.
I tried firewater method too but it didn't work.
I followed these commands -
adb reboot
adb wait-for-device push firewater /data/local/tmp
adb shell
su
chmod 755 /data/local/tmp/firewater
/data/local/tmp/firewater

Nothing happens after last step.

1 .So the question is do i need to go back to nearly stock Rom like ARHD to even try this S-off method. I see v84 of the Rom which is 4.4.3 sense with Sense 6 or do i need to go to older Rom?

2 . Or can S-off method can work after flashing CM or it is necessary to flash Sense ROM only?

3. I was very much interested in running Sense 6 on top of lollipop but read Lollipop not booting because we need to update firmware to latest to run it otherwise it won't boot. Can anyone confirm this ?