Erudite

You got that backwards, Xianxia genre is one who started it - probably because of the 7000-year itch that happened to characters enjoying extremely long lifespan.
Only a minority of traditional Wuxia works has polygamous relationships.

I think my explanation above is clear enough - when you cut a drama, it implies scenes are deleted - so it means later scenes in the DVD will turned up earlier in the TV version.
Hunan TV has a bad reputation for its cuts in other dramas before.

Started filming in August 2018.

Wan Mei has an innate gift of intuitive perceptive structuring.
This is demonstrated in Episode 3, 19 and 32.
The reason why Xing Feng embedded the code that way because he saw her ability in Ep 3 and knew it's only a matter of time before she would see it.
She did not recognize it because a lie has prevented her from connecting the structures.

For example, consider a person who see a tree everyday, and know every structure units of the tree by heart.
One day, someone tell the person to make a plough. The person then suddenly visualize the branches of the tree cut down to make the handles and beam of a plough. He now recognizes the structures in a completely different context.

Can the Duke recognize it too? Possibly, given the same information, but not before Wan Mei and there is evident from his reactions in Ep 19 and 32 that he is not as gifted as Wan Mei in this area.

For further plots on 2nd season, see also my spoiler tagged answer to LalaCandyLand08 below.

@LalaCandyLand:
The Duke's plan is call "Killing multiple birds with one stone":

1. As Chang An pointed out to the Duke in Ep35, the King must see a need to give Duke command of an army. Chang An's pact with the Duke is the army of Chu will support the Duke against the Liang kingdom. In return, the Duke will not take any action against the forces of Chu.
2. In Ep36, the Duke take advantage of the pact in (1) to defeat Liang within 6 months after Chang An's disappearance.
3. The King and most likely Wan Mei is unaware of the pact in (1).
4. After (2) the King turned Emperor begin to contemplate taking away the Duke's army command.
5. If the Duke assassinate the Emperor, the frontier army commanders will revolt declaring themselves kings or join other kingdoms, causing a 2nd interregnum within the Empire.
6. The Later Tang frontier armies are strong but they are stationed against powerful external enemies like Khitans in the North. Moving them is bad news for everyone in China, Wan Mei hinted that when she faced the King the 1st time after her dance in Episode 24.
7. Chang An is in an Northen Frontier City at end of the drama.
8. The Duke need a way to keep his own army and since pact (1) is no longer useful to him after events in (2) he can deal with remnants of Chang An's armies in Chu.
9. By implying that Wan Mei is the legimate successor to the original Tang dynasty he will irk Chang An's supporters in Chu, causing tensions and conflicts with new (Later) Tang Empire allowing him to keep his expeditionary army against Chu.
10. As you said, the Emperor will be upset with rumours with Wan Mei, as she was given the authority to control the provincial army of her region if necessary with her Emblem of Lotus.
11. The Duke tries to gain back some leverage with Wan Mei, since he has no authority over Gui Hua, once Wan Mei become Magnate.
12. The Duke will never gave up trying to be Emperor, it's his 3rd and final promise to his dead mother.
13. In the drama, the most important and influential woman in Duke Li Siyuan life is his mother

Filming began on July 18, 2018 in Beijing.

There is no cliff-hanger. The story is standalone complete whether there is a sequel or not. You can think of the story as a journal of 3.5 years of the leads' lives where there are a number of possible futures where the characters are unaware of but audience knew can happen from hindsight thru their (our) viewpoint and historical events that will happened in the characters' future.

@Lullina: All these are just my thoughts. But what I can think of, the BR creators can too.
A web-movie is a movie that will not be shown in cinema but available for streaming exclusively for VIP members initially then for free by everyone afterwards - exactly the same as our BR drama now. A 2 hour+ long movie has the content of 3 x 40+ mins drama episodes.
1. It's easier for them to write 2 hrs of quality new content versus 25 hours. A shorter wait for the sequel.
2. The shorter project time for a web-movie versus 30+ episodes mean more likely to find schedule to assemble the current team.
3. Higher budget per min for CGI and post-production.
4. Following the timeline of BR, we know something is going to happen to the Emperor historically. Most of us has an expectation of how things are going to turn out for the leads. It probably would entitled a scenery change for the story to progress ;)

lol, of course not - don't let your imagination run wild :p

Nothing has been official.
But I think one possibility would be a web movie as a sequel - I also suggested this earlier for Tribes and Empires (for T & E it might be the only way for a proper conclusion).
I worked out that for BR sequel, it is doable with a budget of 10 episodes for contents of 3 episodes in a web movie. I calculated from figures I have on current ROI for China web-movies the investors might be willing to risk up to a budget cap of equivalent to 15 episodes of BR for a 3 episodes long web movie sequel.
The best comparison is https://kisskh.at/26388-the-fate-of-swordsman, a Wuxia web-movie set on Tang Dynasty with a equally well established world view and characters for its fans (online game players).
The entire movie with Eng subs can be viewed here:
https://www.youtube.com/watch?v=ZKqUoL3h74Q
produced at a cost of 4 to 6 episodes of BR. This web movie of around 1 episode long was meant to be the pilot episode of a future drama series. It broke even easily on VIP fees and ads.

@Lullina: While some of the people at the top of this project has been old friends, most of the cast and crew has never worked or met each other before and only gathered together for this project.
The only likely way for them to all team up again is for a sequel ;)

1. Duke (that's the proper translation) Li Siyuan probably brought back Yue Ying's umbrella [*] to be hanged up above the Shrine of Perfection because Yue Ying wish to commemorate that she has retired as assassin supreme.
She, Wan Mei , Liu Guang and most assassins regard the place to be a sacred memorial.
2. The scene of the Duke carrying an assassin umbrella alone in his final scene and that Wan Mei commented casually that he has 'Mei' (Allure) a few episodes back is probably for audience to reflect that the Duke is in some ways a male Gui Hua assassin master and Yue Ying was his shadow.

[*] Actor Wang Duo confirmed that the umbrella he carried on his final scene is meant to be Yue Ying's

Yes, happy ending for the leads.

The DVD version is what is called the director's cut approved by SART. The TV cut version is a subsequent cut for release by Hunan TV. Scenes might be tweaked in the TV version for whatever reason, including for allowing better continuity after a commercial break.
I watched parts of a few episodes from an international release TV version and didn't spot any major difference from the DVD version.

Disregarding whether this drama adaptation is faithfulness to its source, the first 4 episodes I watched still ranked among the best Xiuzhen drama I have seen. Character introductions are handled smoothly and director Yu Rong Guang maintained decent pacing of the story and transition of scenery.
The visual effects in FBS are pretty good, given that its budget is smaller than https://kisskh.at/20604-martial-universe adapted from the same author. The main VFX company is the same one who did https://kisskh.at/17023-tribes-and-empires-storm-of-prophecy. In the past it even took on some outsourced work from Hollywood (some scenes from 2012 and Fast and Furious 5)

No, the context of 'insert k scene' is obviously to the writer's "future works as a screen writer" not to a specific drama :p

Yes, I just got back - and have a bit of work to catch up to. But assuredly it will be done, if perhaps a bit later than I anticipated :p

Actually this is the oldest Ever Night promotional trailer made from raw footage after the first 10 days of filming (roughly 4 episodes).
The released drama series should began exactly the same as the novel, with the prologue and the first line voice-over by Adam Cheng ('Fuzi' in the drama).

The first line of the drama (and novel) translated should be:
A long, long time ago, the world was filled with many mysterious lands,
and inside those mysterious lands there were many unfathomable people.

BTW, this is only the 2nd time Adam Cheng used his own voice for a C-drama. The last time he spoke Mandarin in a C-drama was 11 years ago.

Competition for C-dramas produced for aired on TV station is so fierce since 2017 that today even the producers cannot tell you whether they can made it until just weeks or days before release date.
The advantage of being able to air on prime-time TV networks is that for most productions, they are almost guarantee to make money back for their investors just from TV royalties.
Web-only dramas can only earned back thru paid subscriptions, product placements and advertisements.

His name is Su Xiao Ding. Search for my reply to Lilly1008's comment below for further details of him - I don't like to retype on mobile while I travel. The character he played including quaintness is partly based on the real King Li Cun Xu (Emperor at EP36).