RBF

Might be Biluo, though there are other cave/underground locations in the second arc, too.

Wang Yilun (Riley Wang) in makeup today: https://www.douban.com/group/topic/301191319/?_i=6544246Dp8_-3B

And another video from the yesterday's opera set rehearsal: https://www.xiaohongshu.com/explore/65b593cc000000002d0014b5
They actually have live musicians there 😃

Few more pics of Fang Yilun in full costume: https://weibo.com/7879144770/NDVbVdWyR

Yes, anyone on internet can put any logo on those pics. The official copyright holders usually let them be, cuz free exposure.
The only time they really start to care is when the reposted stuff is edited in an unflattering way. There were some posts by antis and black marketing accounts that got blocked by weibo on copyright infringement grounds.
About the posts from actors' studios, like with LYX, Ao Ziyi, Bao Shangen, and Xie Bayi, they were definitely greenlit by the drama's promo team but were still put together by the actors' own crews. Some of these posts had SLY's title on the vids or photos, but others hadn't.

White and gold suits her so well

Apart from the booting ceremony pics, none of the bts photos so far were from SLY's official promo team. So it's up to whoever publishes the leak what text to put on it. The weibo account from the link above is just unofficial fan account.
The first batch of official materials is rumored to come around the Chinese New Year (so probably Feb 9 or 10).

Yeah, opera is kinda a theme for a certain villain faction (which people migh've already guessed by their makeup and costumes).

Should be 4 episodes altogether.

Some bts videos of LYX from today:
https://www.xiaohongshu.com/explore/65b35952000000000c005e4f
https://www.xiaohongshu.com/explore/65b36d12000000000f036621
https://www.xiaohongshu.com/explore/65b37d0e000000000a03171c

wirework:
https://www.xiaohongshu.com/explore/65b350b5000000001003ffe4
https://www.xiaohongshu.com/explore/65b34e4d00000000110040a5

farewell at the end of the filming day:
https://www.xiaohongshu.com/explore/65b39008000000002c03fa2c

New episode of LOL mini-series dropped today: https://www.youtube.com/watch?v=58FXuqfjuxE
And Luo Yunxi's studio also posted a bts video: https://weibo.com/6272607759/NDCKGeA31

Fang Zhou's actor finally spotted, it's Zhang Junning (Johnny Zhang): https://www.douban.com/group/topic/301072819/?_i=6267938Dp8_-3B

A few new bts of Xie Binbin (Yu Furen) and Bai Shu (Xue Xianzi): https://weibo.com/7879144770/NDt3ThpTk

Some pics of Xie Binbin from yesterday: https://weibo.com/7879144770/NDekTaimj
His new costume looks great

No. There are some romantic subplots, but it's not a romance story at its core.

Yupp. It usually only becomes known when the drama obtains a distribution license.

Must be this link: https://www.xiaohongshu.com/explore/65abdc43000000001100078f

Li Jiahao in costume: https://www.douban.com/group/topic/300813066/?_i=5713233Dp8_-3B

Some new bts photos of Xie Binbin: https://weibo.com/u/7879144770

SLY extra vloging about his filming day: https://www.douyin.com/video/7324700326148181284