re: installing custom ROM without bootloader unlock
Can someone enter the room without opening of door??
On some Android devices this is possible. Just not on the Moto Quark. This is not relevant for the Moto Maxx XT1250, Moto Maxx XT1225, Moto Turbo XT1225 Quark variants -- which have easily unlocked bootloaders via free code from Motorola, but is very relevant with Verizon locked-down bootloader on the Droid Turbo XT1254.
People new to the Motorola phones don't know it's different from other phones like LG. So, yeah, the question gets tiring.
"Do I need to unlock the bootloader? I just want root!" On these Motorola phones, to write to the system, install custom ROMs
you have to unlock the bootloader.
I'm very familiar with LG LG2 and LG G3 phones, where here in the U.S. AT&T carrier has the bootloader locked down.
There are many 1-click rooting processes available for LG phones. Then you can install TWRP with autorec or
TWRP manager. And then, through TWRP you can install custom ROMs.
No need to unlock the bootloader!
Root AT&T LG G3 D850 and Install TWRP Recovery
http://www.droidviews.com/root-att-lg-g3-d850-and-install-twrp-recovery/
I've helped many friends do this, as LG (at least until the LG G5, which I don't like) made great phones: fantastic specs with very slim bezels.
- The 2012 LG Optimus G (aka G1) was the twin of the LG Nexus 4.
- The 2013 5.2" 1080p LG G2 was the basis for the LG Nexus 5 (shared many same components and specs).
- The 2014 5.5" LG G3 1440p, 3GB RAM and 2015 5.5" LG G4 1440p, 3GB RAM -- both with laser autofocus rear camera with OIS, Qi wireless capabilities. microSD card -- are excellent phones.
I just helped three friends get new (2014) LG G3 phones (new overstock inventory) within the past few weeks -- one Verizon, two AT&T. Bootloaders are NOT unlocked but custom ROMS are still easily installed.
Motorola phones are different. Bootloader has to be unlocked.
________
Added commentary:
For some reason Samsung gets the sales, but LG really has the innovation (or did until the LG G5). They were on a serious winning streak, with through the LG G1 - LG G4.
But
Motorola with the 2014 Quark and the whale Nexus 6 finally made "world class" phones that could compete with Samsung and LG in specs and innovation. Seriously, for awhile it seemed Motorola copying LG's previous phone for their "new" phone:
- The 2013 4.7" 720p Moto X was almost a carbon copy of the 2012 4.7" 720p LG G1 (which admittedly was a good phone), while everyone else that year (LG, Samsung, Sony, etc.) was going to at least 5" 1080p. (The 2013 5.2" 1080p LG G2 was released the same time as the 2012 4.7" 720p Moto X. Originally, Moto tried to charge premium price for that phone, even though it only had mid-tier hardware specs, not even a Snapdragon 8xx chipset. Finally, when Motorola lowered the price it started to sell. Everyone remebers the 2013 Moto X fondly, but compared to the 2013 LG G2 -- on which the Nexus 5 was based -- it was no contest. It was an excellent mid-tier phone, not a top tier phone like the LG G2.)
- Then the 2014 Moto X was a blatant copy of the excellent 2013 5.2" 1080p LG G2. (and the 2013 G2 still had a bigger battery than the 2014 copycat Moto X.)
Motorola tried to correct their 2013 4.7" 720p mistake, but then LG released the 2014 1440p 5.5" LG G3 the same time Motorola released a copy of LG's 2013 1080p phone. 
In 2014 LG meanwhile had moved on to
1440p and other innovations like laser-autofocus with the LG G3.
It was embarrassing if you really knew the smartphone industry, weren't just a blind Motorola fan and/or could only use Verizon phones.
Finally by the end of 2014, with the Quark and Nexus 6 Motorola made two phones which were not direct ripoffs of a previous LG phone, and were
truly excellent in hardware specs. With the Quark, Motorola proved they could really compete and win.
I really, really like the Quark phone. Last summer, I actually won a
2015 LG G4 phone in a contest. 5.5", 1440p, 3GB RAM, rear camera OIS, laser auto-focus camera. FREE! At that point I had two 2014 Quarks already (for me and my wife), but here was a new 2015 LG G4! (and yes you can add Qi wireless sticker to the AT&T LG G4 and it works).
Yet, I sold that 2015 LG G4 and bought another 2014 Quark.

I now own three Moto Maxx XT1225 -- the 3rd is a backup still new in the box. (with rear camera OIS and stereo speakers would be PERFECT). The Moto XT1225 with all the AT&T LTE band and Brazil LTE bands (we visit Brazil almost every year) was the deciding factor.
The Quark was what Google should have released as the gen6 Nexus. It was the "mainstream" size phone that would have sold very well! And would have had tons of dev support, even more than we have now. A 6" display in 2014 was just a huge mistake, and set back the Nexus program so much. For 2015 and 2016 Google basically admitted their mistake by making their displays on their 1440p phones smaller (5.7") and even smaller (5.5") -- more what most people really want.
Google was actually testing a 5.2", 1440p version of the Nexus 6 as late as mid-August 2014... but then went with the whale. They could have easily released TWO sizes (both with top tier specs) and let people choose the winner.

It's easy to see Motorola was developing the Quark/Shamu simultaneously, very much like LG had developed the LG G1/Nexus 4 and and LG G2/Nexus 5. They gave Google the choice of 5.2" like the Quark or 5.95" and Google made the wrong decision...
Google lost me as a Nexus fanboi with the Nexus 6 size decision and changing the name to "Pixel" doesn't fool me.

It wasn't price, it was size. I paid about $700 average for my first two Quarks.
Even today, MY Quarks with 64GB storage, 3GB RAM, 5.2" 1440p AMOLED display competes very well with 2016 phones!
But in 2016 LG screwed up with the LG G5 and the silly "mods". Recommending reasonable cost phones to friends, I still go with "new" 2014 LG G3 ($135) and 2014 LG G4 ($185 - $235), all with free shipping from Hong Kong. You can buy such phones new in the box from excess inventory from Hong Kong via eBay, even Verizon models. And both those phones have even Marshmallow stock now. (But if you want to mod them and install custom ROMs, easier to root and install TWRP with the Kitkat/Lollipop versions out of the box instead of taking the OTA updates.)
While I love the Quark, most of my friends are not Verizon customers and the Moto Maxx XT1225/Moto Turbo XT1225 is not easily available "new in box" at a reasonable price. I can't recommend "used" phones for my friends. I don't know the history and they would blame me if they got a bad phone. For friends who are Verizon customers, yes
NEW Droid Turbo XT1254 are available -- in both 32GB ($195) and 64GB ($215) sizes -- but then you have to factor in the extra $25 for Sunshine.... Even for my Verizon friends, if I'm the one doing the tech support, it's easier for me to recommend LG G3 or LG G4 (with microSD card, Qi wireless and free root and TWRP). I can't justify the extra cost for them and hassle for me for a phone I won't be using. [emoji14]
I chose the Quark for myself and my wife, but it's not the best choice for everyone.
I was hoping Motorola would release a top tier 2016 "Droid Turbo 3/whatever international model" like they did the 2014 Quark and 2015 Kinzie. I would buy the international model which would have easily unlocked bootloader and AT&T bands.

The 2015 Kinzie didn't address the "mistakes" of the 2014 Quark (no rear camera OIS, no stereo speakers) and wasn't enough of an update spec-wise.
Also, the here on XDA the Moto X Force (international Kinzie) has almost no dev support and the Droid Turbo 2 (Verizon Kinzie) bootloader was never unlocked. The Kinzie was a loser. [emoji14]
Then Motorola messed up with the Moto Z Force, making it a true Verizon exclusive (except for a Chinese model that only has Chinese LTE bands). Plus, I still don't want any stinkin' mods.
So, right now this Quark is still the best phone for me.